Actelion announces results of the MAESTRO study with macitentan in patients with pulmonary arterial hypertension due to Eisenmenger Syndrome

Actelion Pharmaceuticals Ltd / Actelion announces results of the MAESTRO study with macitentan in patients with pulmonary arterial hypertension due to Eisenmenger Syndrome . Processed and transmitted by Nasdaq Corporate Solutions. The issuer is solely responsible for the content of this announcement.

ALLSCHWIL/BASEL, SWITZERLAND - 23 January 2017 - Actelion Ltd (SIX: ATLN) today announced that the MAESTRO study to assess the efficacy, safety and tolerability of macitentan in patients with pulmonary arterial hypertension (PAH) due to Eisenmenger Syndrome did not meet its primary objective.

Professor Nazzareno Galiè, Head of the Pulmonary Hypertension Center at the Institute of Cardiology, University of Bologna, and Steering Committee member for the MAESTRO study, commented: "The results of the MAESTRO study are very difficult to interpret. We have seen encouraging positive effects of macitentan in the response of N-terminal pro b-type natriuretic peptide plasma levels and hemodynamic measures. Although the results point towards a benefit of treatment with macitentan, we do not see a significant treatment effect on the primary endpoint of exercise capacity as measured in the 6 minute walk test. I believe this has been influenced by an unexpected improvement in the placebo arm of the study, which is unusual in a predominantly untreated PAH population. In fact, we have not seen such a persistent placebo effect in the multiple studies published so far in PAH. We need to fully analyze the data to understand what could have caused this phenomenon."

In MAESTRO, 226 patients, including 135 patients in Functional Class II, were randomized in a 1:1 ratio to receive either 10 mg macitentan or placebo once daily. After 16 weeks of treatment, the mean change in 6-minute walk distance (6-MWD) from baseline was an increase of 18.3 meters (m) in the macitentan group and 19.7 m in the placebo group. The 6-MWD least-squares mean difference at Week 16 was -4.7 m between macitentan and placebo (95% CL: -22.8, 13.5 m; p=0.612, intention-to-treat (ITT)). There were 3 patients with missing 6-MWD values at Week 16 in the macitentan group, and imputation of zero meters at Week 16 was applied. In the per-protocol population (200 patients), the mean change in 6-MWD from baseline was an increase of 30.2 m in the macitentan group and 18.9 m in the placebo group. The 6-MWD least-squares mean difference at Week 16 was 6.4 m between macitentan and placebo (95% CL: -7.0, 19.8 m; p=0.347 per-protocol).