The U.S. Food and Drug Administration has approved the new drug Opsumit (macitentan) for treatment of adult pulmonary arterial hypertension (PAH), a chronic and debilitating disease that can lead to death or the need for a lung transplant.

PAH is high blood pressure that occurs in the arteries connecting the heart and lungs. It causes the right side of the heart to work harder than normal, which can lead to exercise limitations and shortness of breath. Opsumit belongs to a class of drugs known as endothelin receptor blockers, which can relax the pulmonary arteries, decreasing blood pressure in the lungs.

The safety and effectiveness of Opsumit was established during a long term clinical trial that included 742 participants who were randomly assigned to take either Opsumit or a placebo. The average treatment duration was about two years. In the study, Opsumit was effective in delaying progression of the disease.

Similar to other members in the same drug class, Opsumit carries a Boxed Warning alerting both patients and health care professionals that the drug should not be used in pregnant women because it could potentially harm a developing fetus. Female patients can only receive the drug through the Opsumit Risk Evaluation and Mitigation Strategy (REMS) Program. The REMS program requires prescribers to be certified by enrolling in the program and all female patients must be enrolled and comply with pregnancy testing and contraception requirements before beginning treatment. Pharmacies must also be certified to dispense Opsumit to patients who are authorized to receive it.

Observed side effects in those treated with Opsumit included anemia, common cold-like symptoms, sore throat, bronchitis, headache, flu and urinary tract infection.

Opsumit is marketed by San Francisco-based Actelion Pharmaceuticals US, Inc.