Actelion Reports Its PAH Treatment, Macitentan, Aiding CTEPH Patients in Phase 2 Study

Patrícia Silva, PhD avatar

by Patrícia Silva, PhD |

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Actelion announced that a Phase 2 clinical trial evaluating its pulmonary hypertension treatment, macitentan, in patients with inoperable chronic thromboembolic pulmonary hypertension (CTEPH) has met its primary endpoint. At week 16, treatment resulted in a significant reduction in pulmonary vascular resistance (PVR) compared to placebo.

MERIT is a 24-week, randomized and placebo-controlled, double-blind Phase 2 clinical trial (NCT02021290) evaluating the efficacy, safety and tolerability of macitentan as a treatment for inoperable CTEPH. (Macitentan, under the brand name Opsumit, by Actelion, is FDA-approved to treat pulmonary arterial hypertension [WHO Group I] patients.)

It’s primary endpoint is the change in pulmonary vascular resistance (PVR) at rest, at week 16, compared to baseline. Secondary endpoints include changes from baseline to week 24 in exercise capacity (6-minute walk distance or 6MWD), in the Borg dyspnea index collected at the end of the 6MWD test, and the proportion of patients with disease worsening.

In the trial, 80 patients received either macitentan 10 mg once daily (40 patients) or placebo (40 patients).

Results showed that at 16 weeks, treatment induced a 16 percent reduction in PVR compared with placebo. This was observed across all patients sub-groups, including those using a background pulmonary hypertension therapy at baseline (61 percent), including PDE-5 inhibitors (59 percent).

After 24 weeks, results also showed a significant increase in treated patients’ exercise capacity, with a mean change in the 6MWD from baseline of 35 meters in this group, compared to one meter in placebo-treated patients.

Safety analysis demonstrated that macitentan treatment was well-tolerated by patients, with adverse events similar to those seen in previous clinical trials. The most commonly reported adverse events — peripheral edema and anemia — occurred with a higher frequency in macitentan-treated patients than in those given placebo. Those findings were consistent with the treatment’s known safety profile from previous clinical studies. There was no increase in liver aminotransferases (liver enzymes) greater than three times the upper normal limit seen, and only placebo patients chose to discontinue treatment.

“Inoperable chronic thromboembolic pulmonary hypertension is associated with a poor prognosis if left untreated, and additional therapeutic options are needed for these patients who are not candidates for surgery,” Guy Braunstein, head of Global Clinical Development at Actelion, said in a press release. “I am very pleased that the study has shown a significant decrease in PVR with macitentan and by the significant improvement in exercise capacity. I would like to thank everyone who has participated in this study. The company will now fully analyze the data and discuss the findings with health authorities.”

Actelion will present full trial results at an upcoming medical meeting and in a peer-reviewed publication.

Opsumit is an orally available endothelin receptor antagonist for the treatment of pulmonary arterial hypertension (PAH). The product is commercially available in over 35 markets, including the U.S. (since November 2013), Germany (since January 2014) and Japan (since June 2015). Registration processes for other countries is ongoing.