Opsumit (macitentan)
An approved treatment for Pulmonary Arterial Hypertension.
The same compound appears under different names depending on the context. Here is how to identify Macitentan wherever you encounter it, plus the key facts at a glance.
- Generic name
- Macitentan
- Brand name
- Opsumit
- Development code
- ACT-064992
- Drug class
- Endothelin receptor antagonist
- Manufacturer
- Janssen (Johnson & Johnson)
- How it's taken
- Taken as a single oral tablet once daily (10 mg).
An oral endothelin receptor antagonist for adults with PAH (WHO Group I) that blocks both ETA and ETB receptors. It is not approved for children; a trial in children ages 2 to 17 did not show a benefit. Also available in a fixed-dose combination with tadalafil (Opsynvi) as the first single-tablet PAH combination therapy.
Where Macitentan fits
Preferred endothelin receptor antagonist for many PAH patients due to improved efficacy data and once-daily dosing. Commonly used in combination with PDE5 inhibitors and/or prostacyclins.
How Macitentan works
Endothelin-1 is a powerful blood vessel constrictor that's overproduced in PAH. It drives both vasoconstriction and abnormal cell proliferation in pulmonary arteries through ETA and ETB receptors. Macitentan blocks both receptor types, reducing vessel constriction, slowing vascular remodeling, and improving blood flow through the lungs.
Mechanism: Dual endothelin receptor antagonist that blocks vessel-constricting endothelin signaling
Side effects and safety
Anemia, stuffy nose or sore throat, bronchitis, headache, flu and urinary tract infection are the most common. Must not be used in pregnancy (boxed warning; pregnancy test before starting). Drugs in this class can cause liver injury and liver failure, so liver tests are done before starting and repeated during treatment as needed; report nausea, vomiting, pain in the upper right belly, tiredness, loss of appetite, yellow skin or eyes, or dark urine right away. The label also warns about fluid buildup and swelling (which has led to hospital stays for heart failure), fluid in the lungs in people with pulmonary veno-occlusive disease, and lower sperm counts. Decreased hemoglobin is a class effect.
This is not a complete list of side effects. Talk to your doctor or pharmacist about what to expect and when to seek medical attention.
Taking Macitentan
Taken as a single oral tablet once daily (10 mg). Also available as OPSYNVI (macitentan + tadalafil combination tablet, approved March 2024). For anyone who could become pregnant, a pregnancy test is required before starting, and effective birth control is needed before starting, during treatment and for 1 month after stopping.
Availability and cost
Generic versions may be available at a lower cost. Ask your pharmacist.
Next-generation endothelin receptor antagonist designed for improved tissue penetration and sustained receptor binding compared to bosentan. Generic macitentan tablets from several manufacturers became available in 2026, which can lower cost compared with brand Opsumit.
Help paying for Opsumit
Pick your insurance to see which help fits. Drugmaker copay cards can't be used with Medicare, Medicaid or TRICARE; charity funds are the usual route there.
- Copay help
Eligible commercially insured patients pay $5 per fill; yearly maximum shared across J&J oral PAH medicines. Not valid with Medicare, Medicaid or other government programs.
For: private insurance · source - Free medicine program
Uninsured patients, or those whose insurance does not fully meet their needs, may get the medicine free for up to one year if they meet income and eligibility rules.
For: no insurance, underinsured, private insurance, Medicare, Medicaid · source - Insurance and case manager help
Care Coordinators explain insurance coverage and out-of-pocket costs and identify cost support options.
The official page does not say who qualifies. Ask the program. · source
Good to know: PAH Companion withMe is an education program, not cost support; cost help is through J&J withMe. Cost help is J&J withMe. Terms for free drug at PatientAssistanceInfoPH.com.
- From a charity · HealthWell FoundationPulmonary Hypertension (Medicare Access) fundOpen
Pays for: Copays, premiums or other treatment costs. Medicare patients only.
- From a charity · TotalAssist (formerly PAN Foundation)Pulmonary Hypertension fundOpen
Pays for: Out-of-pocket costs for approved medications, up to $9,500 per year. Requires health insurance (any kind).
- From a charity · The Assistance FundPulmonary Hypertension fundWaitlist
Pays for: Copays, coinsurance, deductibles and other health-related expenses.
The foundation says: “WAITLIST — Accepting Waitlist Patients. TAF is currently accepting requests to join the enrollment waitlist for this program. Waitlists a…”
Clinical trial results
SERAPHIN Phase 3 trial (742 patients) showed 45% reduction in morbidity and mortality events versus placebo over long-term treatment. OPSYNVI combination demonstrated bioequivalence to individual components with improved adherence.
Development history
Approved by FDA in October 2013. Designed as an improved endothelin receptor antagonist with tissue-targeting properties. The OPSYNVI combination tablet (approved March 2024) simplifies treatment as the first once-daily single-tablet PAH combination.
Explore Pulmonary Arterial Hypertension trials
Other Pulmonary Arterial Hypertension treatments
Common questions about Macitentan
▸What is Macitentan (Opsumit)?
An oral endothelin receptor antagonist for adults with PAH (WHO Group I) that blocks both ETA and ETB receptors. It is not approved for children; a trial in children ages 2 to 17 did not show a benefit. Also available in a fixed-dose combination with tadalafil (Opsynvi) as the first single-tablet PAH combination therapy.
▸How does Macitentan work?
Endothelin-1 is a powerful blood vessel constrictor that's overproduced in PAH. It drives both vasoconstriction and abnormal cell proliferation in pulmonary arteries through ETA and ETB receptors. Macitentan blocks both receptor types, reducing vessel constriction, slowing vascular remodeling, and improving blood flow through the lungs.
▸What are the side effects of Macitentan?
Anemia, stuffy nose or sore throat, bronchitis, headache, flu and urinary tract infection are the most common. Must not be used in pregnancy (boxed warning; pregnancy test before starting). Drugs in this class can cause liver injury and liver failure, so liver tests are done before starting and repeated during treatment as needed; report nausea, vomiting, pain in the upper right belly, tiredness, loss of appetite, yellow skin or eyes, or dark urine right away. The label also warns about fluid buildup and swelling (which has led to hospital stays for heart failure), fluid in the lungs in people with pulmonary veno-occlusive disease, and lower sperm counts. Decreased hemoglobin is a class effect.
▸How is Macitentan taken?
Taken as a single oral tablet once daily (10 mg). Also available as OPSYNVI (macitentan + tadalafil combination tablet, approved March 2024). For anyone who could become pregnant, a pregnancy test is required before starting, and effective birth control is needed before starting, during treatment and for 1 month after stopping.
▸Is Macitentan FDA approved?
Yes, Macitentan (Opsumit) is FDA approved (2013) for the treatment of Pulmonary Arterial Hypertension.
▸What makes macitentan different from bosentan?
Both are dual endothelin receptor antagonists, but macitentan was specifically designed to improve on bosentan's limitations. Macitentan has enhanced tissue penetration and sustained receptor binding, potentially providing more effective blockade of endothelin signaling in pulmonary artery walls. Critically, macitentan has a lower risk of liver toxicity than bosentan, eliminating the need for monthly liver function testing. The SERAPHIN trial also showed reduction in morbidity and mortality events, which bosentan's trials did not demonstrate.
▸What is Opsynvi?
Opsynvi is a fixed-dose combination tablet containing macitentan (10 mg) and tadalafil (40 mg) approved in March 2024. It is the first single-tablet PAH combination therapy, simplifying the regimen for patients who take both an endothelin receptor antagonist and a PDE5 inhibitor. Instead of taking two separate pills, patients take one Opsynvi tablet daily. The combination has been shown to be bioequivalent to taking the individual drugs separately.
▸What did the SERAPHIN trial show?
The SERAPHIN trial enrolled 742 PAH patients, with a median treatment exposure of about 2 years and up to 3.6 years, making it one of the longest PAH outcome trials. Macitentan 10 mg reduced the composite of morbidity/mortality events by 45% compared to placebo. The reduction was driven by decreases in both disease worsening and PAH-related hospitalizations. This long-term outcome data distinguishes macitentan from bosentan, which did not demonstrate similar event-driven outcomes.
▸Does macitentan require liver monitoring?
While liver function monitoring is recommended, macitentan does not require the mandatory monthly liver testing that bosentan does. However, the label warns that drugs in this class can cause liver injury and liver failure, and liver injury has been reported with macitentan, so liver tests are needed before starting and should be repeated during treatment as your doctor directs.