Merck (MRK.N) said on Thursday the U.S. health regulator will review its experimental therapy to treat a type of progressive blood vessel disorder on a priority basis.

The drugmaker had gained rights to the therapy, sotatercept, through its $11.5 billion acquisition of Acceleron Pharma in 2021.

The U.S. Food and Drug Administration has set March 26, 2024 as a target action date for the review, Merck said.

If approved, the therapy will help the U.S. drugmaker diversify its revenue stream as its blockbuster cancer immunotherapy, Keytruda, moves towards loss of market exclusivity in 2028.

Merck’s application is based on data from a late-stage study in which sotatercept, combined with a background therapy, helped patients with pulmonary arterial hypertension (PAH) to walk about 40.8 meters more in six minutes.

Sotatercept could also be the first treatment of its class, which targets a type of protein called activins that lead to higher levels of follicle-stimulating hormone associated with the disease.

J.P. Morgan analyst Chris Schott had estimated the therapy to reach peak sales of $3 billion to $4 billion.

Merck had said it expects PAH to be a roughly $7.5 billion market by 2026 when it announced the Acceleron deal.

Adempas belongs to a class of drugs known as soluble guanylate cyclase stimulators that help arteries relax to increase blood flow and decrease blood pressure. It generated sales of $238 million for Merck in 2022, according to LSEG data.

PAH is a rare, progressive disorder characterized by high blood pressure in the arteries of the lungs.

About 500-1000 new cases of PAH are being diagnosed each year in the U.S., according to government data.