Efficacy and safety of the endothelin-1 receptor antagonist macitentan in epicardial and microvascular vasospasm; a proof-of-concept study

Background: Treatment of patients diagnosed with angina due to epicardial or microvascular coronary artery spasm (CAS) is challenging because patients often remain symptomatic despite conventional pharmacological therapy. In this prospective, randomized, double-blind, placebo-controlled, sequential cross-over proof-ofconcept study, we compared the efficacy and safety of macitentan, a potent inhibitor of the endothelin-1 receptor, to placebo in symptomatic patients with CAS despite background pharmacological treatment.Methods: Patients with CAS diagnosed by invasive spasm provocation testing with >3 anginal attacks per week despite pharmacological treatment were considered for participation. Participants received either 10 mg of macitentan or placebo daily for 28 days as add-on treatment. After a wash-out period patients were crossed over to the alternate treatment arm. The primary endpoint was the difference in anginal burden calculated as [1] the duration (in minutes) * severity (on a Visual Analogue Scale (VAS) pain scale 1-10); and [2] the frequency of angina attacks * severity during medication use compared to the run-in phase.Results: 28 patients of whom 22 females (79%) and a mean age of 55.3 & PLUSMN; 7.6 completed the entire study protocol (epicardial CAS n = 19 (68), microvascular CAS n = 9 (32)). Change in both indices of anginal burden were not different during treatment with add-on macitentan as compared to add-on placebo (duration*severity: -9 [-134 78] vs -45 [-353 11], p = 0.136 and frequency*severity: -1.7 [-5.8 1.2] vs -1.8 [-6.2 0.3], p = 0.767). The occurrence and nature of self-reported adverse events were closely similar between the treatment phase with macitentan and placebo.Conclusion: In patients with angina due to epicardial or microvascular CAS despite background pharmacological treatment, 28 days of add-on treatment with the ET-1 receptor antagonist, macitentan 10 mg daily, did not reduce anginal burden compared to add-on treatment with placebo.Trial Registration https://trialsearch.who.int/, Identifier: EUCTR2018-002623-42-NL. Registration date: 20 February 2019.