In addition to lowering patients’ lung blood pressure, Opsumit also improved their ability to exercise, and was safe, researchers said.
The trail involved CTEPH patients who were ineligible for surgery. Many had already been treated with other CTEPH medications.
Altogether, the results showed that Opsumit is a viable treatment option for the disease, researchers said.
The study was published in the journal The Lancet Respiratory Medicine. It was titled “Macitentan for the treatment of inoperable chronic thromboembolic pulmonary hypertension (MERIT-1): results from the multicentre, phase 2, randomised, double-blind, placebo-controlled study.”
CTEPH is a type of pulmonary arterial hypertension, or PAH. CTEPH’s hallmark is chronic blood clots in the arteries of the lungs.
The U.S. Food and Drug Administration has approved Opsumit for PAH. Actelion decided to test it in CTEPH because abnormalities in tiny lung blood vessels are similar in the two conditions.
Researchers recruited 80 CTEPH patients from hospitals around the globe. They randomly assigned them to either 10 mg of Opsumit once a day or a placebo. Half of the group received Opsumit.
Opsumit patients’ pulmonary vascular resistance scores improved during the 16-week trial. They decreased to 73 percent of initial scores, versus 87 percent in the placebo group.
Researchers said the results meant that the trial met its primary goal of substantially decreasing pulmonary vascular resistance.
The team also measured patients’ ability to exercise after six months. Their yardstick was the six-minute walk distance test — or how far a patient could walk in six minutes.
Those on Opsumit improved their distance an average of 35 meters. Placebo-treated participants’ improvement averaged only 1 meter. Opsumit did not improve shortness of breath, however.
During the trial, three patients in the placebo group ended up in a higher World Health Organization PAH functional class, meaning their disease had worsened. None of the Opsumit group went to a higher category.
Also, 95 percent of the Opsumit-treated patients experienced no progression in their disease, compared with 87.5 percent in the placebo group. In addition, Opsumit improved measures of patients’ heart function.
Seven placebo patients experienced severe adverse events, versus three in the Opsumit group. This suggested the events were linked to the disease rather than the treatment.
The most common adverse events in the Opsumit group were peripheral edema, or swelling, and decreased levels of hemoglobin, a molecule in red blood cells that carries oxygen.
Overall, the MERIT-1 trial show that Opsumit “significantly improved cardiopulmonary hemodynamics [blood flow] and clinical variables in patients with inoperable CTEPH,” researchers wrote. They said studies should be done on whether a combination therapy that included Opsumit can benefit CTEPH patients.