MRK's Winrevair Phase III Study in Newly Diagnosed PAH Meets Goal

Merck MRK announced that the phase III HYPERION study evaluating its pulmonary arterial hypertension (“PAH”) drug, Winrevair (sotatercept), in newly diagnosed intermediate or high-risk PAH patients, met its primary endpoint.

The HYPERION study evaluated Winrevair versus placebo in recently diagnosed adult patients with PAH, WHO Group 1 functional class (FC) II or III at intermediate or high risk of disease progression. The study’s primary endpoint was time to clinical worsening (TTCW) as measured by a composite endpoint of all-cause death, including the need for non-planned PAH-related hospitalization, atrial septostomy, lung transplantation or worsening PAH symptoms.

Data from the HYPERION study showed that treatment with Winrevair added to background PAH therapy within 12 months after initial diagnosis led to a statistically significant and clinically meaningful reduction in the risk of clinical worsening events versus placebo.

In January, Merck announced that the HYPERION study was stopped early and moved to final analysis, based on overwhelming efficacy seen in the phase III ZENITH study and review of available data from the Winrevair clinical program, including the STELLAR study.

HYPERION is the third phase III study on Winrevair to demonstrate significant efficacy in adults with PAH, the first being the STELLAR study, followed by the ZENITH study.

Year to date, shares of Merck have lost 19.4% compared with the industry’s decrease of 2.6%.

MRK Pins Hope on Winrevair Amid Looming Keytruda LOE

Winrevair was approved by the FDA to treat PAH, WHO Group 1, in March 2024 based on data from the STELLAR study. The drug was approved for similar use in the EU in August 2024.

PAH is a rare, progressive blood vessel disorder that affects the blood vessel walls in the lungs, resulting in elevated blood pressure. It exerts significant strain on the heart, as it works harder to pump blood through the lungs, eventually leading to heart failure if left untreated.

Winrevair is designed to target cellular signaling associated with vascular hyperproliferation and pathological remodeling to treat PAH. Winrevair works by blocking the proteins that contribute to the thickening of blood vessel walls in the lungs.

Winrevair generated sales worth $280 million in the first quarter of 2025, increasing 40% on a sequential basis. Per management, Winrevair continues to perform in line with the company’s high expectations in the United States, as evident from a steady increase in new prescription trends. In ex-U.S. markets, MRK is progressing with launches and reimbursement.

Merck is pinning hopes on Winrevair to boost its top line once its blockbuster drug, Keytruda, a PD-L1 inhibitor, loses patent exclusivity in 2028. The company believes that Winrevair has the potential to generate significant revenues over the long term.

Other Players in the PAH Market

Significant players in the PAH market are United Therapeutics UTHR and Johnson & Johnson JNJ.

UTHR markets four drugs to treat PAH in the United States — Remodulin, Orenitram, Tyvaso and Adcirca.

Remodulin is an injectable formulation of treprostinil. Orenitram is an oral version of treprostinil, while Tyvaso is an inhaled version of Treprostinil. UTHR’s Remodulin, Orenitram and Tyvaso recorded sales of $138.2 million, $120.7 million and $466.3 million, respectively, in the first quarter of 2025.

J&J’s key PAH drugs include Opsumit and Uptravi. JNJ recorded revenues of $1.02 billion from its PAH franchise in the first quarter of 2025.

MRK's Zacks Rank & Stock to Consider

Merck currently carries a Zacks Rank #3 (Hold).

A better-ranked stock in the biotech sector is Exelixis EXEL, which has a Zacks Rank #2 (Buy) at present. You can see the complete list of today’s Zacks #1 Rank (Strong Buy) stocks here.

In the past 60 days, estimates for Exelixis’ earnings per share have increased from $2.31 to $2.61 for 2025. During the same time, earnings per share estimates for 2026 have increased from $2.83 to $3.03. Year to date, shares of EXEL have rallied 30.2%.

EXEL’s earnings beat estimates in each of the trailing four quarters, with the average surprise being 48.60%.

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