Merck, known as MSD outside the US and Canada, has received the US Food and Drug Administration (FDA) approval for Winrevair (sotatercept-csrk) to treat pulmonary arterial hypertension (PAH).

Winrevair is an activin signalling inhibitor therapy that works by improving the balance between pro- and anti-proliferative signalling.

The drug is indicated to increase exercise capacity, improve WHO functional class (FC) and reduce the risk of clinical worsening events in adults with PAH (WHO Group 1).

It is administered once every three weeks by subcutaneous injection by appropriate patients or caregivers with training and follow-up from a healthcare provider.

Merck is planning to start commercialising Winrevair in the US, through select speciality pharmacies, by the end of April this year.

Merck Research Laboratories chief medical officer, senior vice president and global clinical development head Eliav Barr said: “PAH remains a debilitating disease with high morbidity and mortality.

“This approval of WINREVAIR is an important milestone and a testament to our science-led strategy and focus on the development of innovations that can help people affected by rare diseases like PAH. We are proud to bring this novel medicine to patients.”

The FDA approval of Winrevair follows the US FDA Breakthrough Therapy Designation and is based on the results from the Phase 3 STELLAR trial in adult patients with PAH.

In the study, the addition of Winrevair to background therapy resulted in an enhanced six-minute walk distance from baseline by 41m at Week 24.

Also, the drug improved several key secondary outcome measures, including reducing the risk of death and worsening events by 84%, compared to background therapy alone.

Winrevair comes with a warning that healthcare providers should monitor haemoglobin and platelets before each dose of the drug, for the first 5 doses or longer if values are unstable.

The drug may increase haemoglobin, leading to erythrocytosis, decrease platelet count and cause severe thrombocytopenia, and foetal harm.

Phase 3 STELLAR study investigator Marc Humbert said: “Pulmonary arterial hypertension is a rare, progressive and ultimately life-threatening disease in which blood vessels in the lungs thicken and narrow, causing significant strain on the heart.

“Based on the Phase 3 STELLAR trial, adding WINREVAIR to background PAH therapy demonstrated significant clinical benefits compared to background PAH therapy alone.

“This approval is an important milestone, as it offers healthcare providers a novel therapeutic option that targets a new PAH treatment pathway.”