Macitentan for the treatment of pulmonary arterial hypertension

Real-world effectiveness and safety of macitentan in patients with pulmonary artery hypertension: a multicenter, retrospective, observational study in China

BACKGROUND

Macitentan, either as monotherapy or part of combination therapy, improved clinical outcomes in patients with pulmonary artery hypertension (PAH) in clinical trials. Evidence on the effectiveness and safety of macitentan administered in real-world clinical practice in China is limited.

METHODS

This real-world, retrospective, multicenter chart review study was conducted at seven hospitals in China. Adult patients with a diagnosis of PAH who initiated macitentan and had medical assessments at 3-7 months after macitentan initiation were included. The primary outcomes were changes in the World Health Organization functional class (WHO-FC), 6-min walk distance (6MWD), and N-terminal pro-B-type natriuretic peptide (NT-proBNP)/B-type natriuretic peptide from baseline to first follow-up visit (months 3-7). Serious adverse events (SAEs) and adverse drug reactions (ADRs) of macitentan were collected.

RESULTS

From 30 August 2021 to 31 March 2022, 214 eligible patients were included in the safety analysis set and 105 patients were included in the analysis of effectiveness. At the first follow-up visit compared with baseline, significant changes in WHO-FC were observed (p = .04), 93.5% patients had their WHO-FC improved (25.8%) or maintained (67.7%). 6MWD changed by a mean (standard deviation [SD]) of 45.0 (81.4) meters (p < .001), with 94.7% having their 6MWD improved (34.7%) or maintained (60.0%). The mean (SD) of NT-proBNP decreased from 1667.4 (3233.0) ng/L to 1090.0 (2230.1) ng/L (p < .001). In the safety analysis set, 24 (11.2%) patients experienced at least one ADR and/or SAE. ADRs and SAEs were reported in 11 (5.1%) and 18 (8.4%), respectively. No deaths or unexpected safety events were observed.

CONCLUSION

This study provided real-world evidence on the clinical benefits and good tolerance of macitentan in Chinese patients with PAH treated in routine clinical practice.

Transfer and Vascular Effect of Endothelin Receptor Antagonists in the Human Placenta

Increasing evidence suggests a role for the ET (endothelin) system in preeclampsia. Hence, blocking this system with endothelin receptor antagonists (ERAs) could be a therapeutic strategy. Yet, clinical studies are lacking due to possible teratogenic effects of ERAs. In this study, we investigated the placental transfer of ERAs and their effect on ET-1-mediated vasoconstriction. Term placentas were dually perfused with the selective ET_AR (ET type A receptor) antagonists sitaxentan and ambrisentan or the nonselective ET_AR/ET_BR antagonist macitentan and subsequently exposed to ET-1 in the fetal circulation. ET-1 concentration-response curves after incubation with sitaxentan, ambrisentan, macitentan, or the selective ET_BR antagonist BQ-788 were also constructed in isolated chorionic plate arteries using wire-myography, and gene expression of the ET-system was quantified in healthy and early onset preeclamptic placentas. At steady state, the mean fetal-to-maternal transfer ratios were 0.32±0.05 for sitaxentan, 0.21±0.02 for ambrisentan, and 0.05±0.01 for macitentan. Except for BQ-788, all ERAs lowered the response to ET-1, both in the perfused cotyledon and isolated chorionic plate arteries. Placental gene expression of ECE-1, ET_AR, and ET_BR were comparable in healthy and preeclamptic placentas, while ET-1 expression was higher in preeclampsia. Our study is the first to show direct transfer of ERAs across the term human placenta. Furthermore, ET_AR exclusively mediates ET-1-induced constriction in the fetoplacental vasculature. Given its limited transfer, macitentan could be considered as potential preeclampsia therapy. Extending knowledge on placental transfer to placentas of preeclamptic pregnancies is required to determine whether ERAs might be applied safely in preeclampsia.

From the Cover: MechanisticInsights in Cytotoxic and Cholestatic Potential of the Endothelial Receptor Antagonists Using HepaRG Cells

Several endothelin receptor antagonists (ERAs) have been developed for the treatment of pulmonary arterial hypertension (PAH). Some of them have been related to clinical cases of hepatocellular injury (sitaxentan [SIT]) and/or cholestasis (bosentan [BOS]). We aimed to determine if ambrisentan (AMB) and macitentan (MAC), in addition to BOS and SIT, could potentially cause liver damage in man by use of human HepaRG cells. Our results showed that like BOS, MAC-induced cytotoxicity and cholestatic disorders characterized by bile canaliculi dilatation and impairment of myosin light chain kinase signaling. Macitentan also strongly inhibited taurocholic acid and carboxy-2',7'-dichlorofluorescein efflux while it had a much lower inhibitory effect on influx activity compared to BOS and SIT. Moreover, these three drugs caused decreased intracellular accumulation and parallel increased levels of total bile acids (BAs) in serum-free culture media. In addition, all drugs except AMB variably deregulated gene expression of BA transporters. In contrast, SIT was hepatotoxic without causing cholestatic damage, likely via the formation of reactive metabolites and AMB was not hepatotoxic. Together, our results show that some ERAs can be hepatotoxic and that the recently marketed MAC, structurally similar to BOS, can also cause cholestatic alterations in HepaRG cells. The absence of currently known or suspected cases of cholestasis in patients suffering from PAH treated with MAC is rationalized by the lower therapeutic doses and Cmax, and longer receptor residence time compared to BOS.