Macitentan (Opsumit(®)) is an orally active, dual endothelin receptor antagonist 
(ERA) with tissue targeting properties. Macitentan was approved recently in the 
EU (as monotherapy or combination therapy) for the long-term treatment of 
pulmonary arterial hypertension (PAH) in adults of WHO functional class II or 
III, and in the USA for the treatment of PAH (WHO group I) to delay disease 
progression and reduce hospitalization for PAH. This article reviews the 
pharmacological properties, efficacy and tolerability data relevant to the use 
of macitentan in this indication. Treatment with macitentan 10 mg once daily 
significantly reduced the risk for the primary composite endpoint of morbidity 
and mortality in patients with PAH (mostly WHO functional class II or III) in 
the large, randomized, placebo-controlled SERAPHIN study. Other efficacy 
outcomes, including exercise capacity, haemodynamic parameters and 
health-related quality of life also improved significantly with macitentan 
relative to placebo. Macitentan was generally well tolerated in this study. As 
with other ERAs, haemoglobin levels decreased with macitentan therapy; however, 
these were not progressive and stabilized following longer-term treatment. 
Although comparative studies are needed to definitively position macitentan with 
respect to other approved agents, current evidence suggests that macitentan is a 
useful treatment option for initial therapy in patients with WHO functional 
class II or III PAH, which has the potential advantage of once-daily 
administration.