Actelion PAH drug misses endpoint in Phase III trial aimed at expanding use

Swiss biotech major Actelion (SIX: ATLN) today released disappointing results from the MAESTRO study to assess the efficacy, safety and tolerability of macitentan in patients with pulmonary arterial hypertension (PAH) due to Eisenmenger syndrome, saying it 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."

Minor impact, according to analysts