PARIS – In a multicenter, placebo-controlledincluding the primary endpoint of pulmonary vascular resistance, according to a late-breaking presentation at the annual congress of the European Respiratory Society.
“This is the first randomized, controlled trial that enrolled only patients with PoPH, and it demonstrates that a therapy used in pulmonary arterial hypertension improves hemodynamics in PoPH,” reported, of the Centre des Maladies Vasculaires Pulmonaires, Université de Paris–Sud, Clamart, France.
PoPH, defined by accompanying portal hypertension, is a variant on pulmonary arterial hypertension (PAH). Liver dysfunction is common but not required for a diagnosis. Although patients often receive therapies known to be effective in PAH, such as drugs in the endothelin receptor antagonist class, prostanoids, or phosphodiesterase-5 inhibitors, there “are very limited data” demonstrating efficacy of any drug specifically for patients with PoPH, according to Dr. Sitbon. One reason is that PoPH has been an exclusion criterion in large PAH treatment trials.
Ina double-blind trial presented by Dr. Sitbon, 85 PoPH patients were randomized to 10 mg macitentan or placebo. Essentially, all were in World Health Organization functional class II or III with a median 6-minute walk distance (6MWD) of about 385 meters. During the trial, patients were permitted to remain on baseline therapies, including prostanoids and phosphodiesterase-5 inhibitors when doses had been stable for at least 3 months prior to randomization.
The primary endpoint was change in pulmonary vascular resistance (PVR) at 12 weeks. Other hemodynamic changes, such as change in cardiac index and total pulmonary resistance, were included in secondary endpoints along with change in WHO class and change in 6MWD.
When compared at 12 weeks with a model-adjusted ratio of geometric means, the ratio of PVR for the treatment to experimental arms was 0.65, which was a 35% relative improvement (P less than .0001) with macitentan.
The relative reduction from baseline in total arterial pressure was also highly significant favoring macitentan (–199.8 vs. –18.3 dyne/sec per cm–5; P less than .0001). Mean pulmonary pressure was slightly increased at the end of 12 weeks relative to baseline in the placebo group (+0.4 mm Hg) but fell 6.4 mm Hg in the treatment group (P less than .0001). In addition, cardiac index improved substantially on macitentan but not on placebo (0.6 vs. 0.1 L/min per m2; P = .0009).
However, there were no significant differences at the end of 12 weeks between groups for change from baseline in WHO functional class or 6MWD. Change in hepatic venous pressure gradient was evaluated in patients with liver disease, but macitentan was not associated with any effect on this parameter.
Macitentan was well tolerated overall. Although one patient experienced a equal to or greater than three times the upper limit of normal elevation of liver enzymes, Dr. Sitbon reported that there were no other hepatic safety concerns. Overall, he characterized the safety of macitentan in PoPH as “consistent with that previously observed in PAH.”
Larger and longer-term trials are needed to evaluate the impact of treatment on clinical events, but Dr. Sitbon indicated that these results demonstrate acceptable safety and tolerability and a favorable effect on hemodynamics. He further suggested that this randomized study provides a first step toward establishing an evidence-based treatment in this disease.
Dr. Sitbon reported financial relationships with Bayer, GlaxoSmithKline, and Actelion, the sponsor of this trial.