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FDA approves Merck lung disease drug acquired in $11B deal

The Food and Drug Administration on Tuesday approved a new Merck & Co. drug to treat pulmonary arterial hypertension. Called Winrevair, the drug is the first treatment that targets the underlying cause of the lung condition, which typically leads to death within a decade of diagnosis.

The FDA’s approval was based on clinical trial data showing Winrevair improved exercise duration and quality of life, as well as delayed death or worsening of the disease.

The shot, known scientifically as sotatercept, blocks proteins that contribute to the thickening of blood vessel walls in the lung and lead to rising blood pressure, an overworked heart and symptoms like shortness of breath, fatigue and chest pain. It’s administered every three weeks.

“Sotatercept is a paradigm shift and a huge step forward in the treatment of PAH,” said Ioana Preston, a study investigator and director of the pulmonary hypertension center at Tufts Medicine, in an interview.

“I’ve had some amazing stories from a few of the patients who I enrolled who went from really impaired and short of breath and very close to being on … rescue therapy, to getting off oxygen and going back to their jobs, and maintaining the improvement for more than a year,” Preston said.

Several types of drugs are are currently used to treat PAH, all of which are vasodilators that help widen blood vessels. Johnson & Johnson’s Opsumit and Uptravi, as well as United Therapeutics’ Tyvaso, are among the products prescribed for the condition.

However, those drugs only curb symptoms, rather than the underlying disease. While they can improve exercise capacity, for instance, they don’t address the biological factors that cause PAH to progress.

“Even with everything that’s out there [these patients] still carry a high mortality rate,” said Joerg Koglin, Merck’s senior vice president of global clinical development.

Winrevair’s approval hinged on a Merck-run trial named Stellar, which enrolled 323 people with PAH who were stable on current medications. The participants were randomized to receive either Winrevair or a placebo once every three weeks. Investigators assessed the drug’s effectiveness based on a commonly used measure in cardiovascular disease called the six-minute walk test.

After six months of treatment, people who received Winrevair walked a median of 34 meters in that test, compared to just 1 meter among those who received a placebo. By one method of estimatation, the difference between the groups in change from baseline was 41 meters — a statistically significant result. Physicians usually consider a difference above 30 meters meaningful.

Winrevair-treated participants also scored statistically better on seven of eight other efficacy measures, including one that evaluated time to death or a “clinical worsening” event. On that score, the relative risk was 84% lower among people who received Merck’s drug instead of a placebo.

The most notable side effect was increased levels of hemoglobin, the oxygen-carrying blood protein. Elevations can lead to blood clots and other health problems. This adverse event was reported in more than 5% of patients, but doctors managed it by interrupting or reducing doses. No participants stopped treatment as a result.

The FDA’s labeling for the drug asks physicians to monitor patient hemoglobin levels before each of at least the first five doses.

People taking Winrevair also experienced other side effects like spider veins and bleeding gums and noses.

Merck acquired Winrevair through an $11.5 billion buyout of Acceleron Pharma in 2021. It’s part of a pipeline that the New Jersey-based drumaker estimates will bring in $35 billion in annual sales by the middle of the next decade.

Citing data company EvaluatePharma, Cantor Fitzgerald analyst Louise Chen expects Winrevair to achieve $2 billion in sales in 2028. Among investors, the range of peak annual sales forecasts ranges as low as $1 billion to as high as $8 billion, Chen wrote in a March 10 note to clients.

A strong launch might reassure investors Merck can overcome the looming loss of exclusivity for its biggest seller, the cancer drug Keytruda. Some of Keytruda’s key patents will expire later in the decade.

Success in two ongoing follow-up studies could be crucial to Winrevair’s market adoption. One, called Hyperion, is evaluating its use in newly diagnosed patients. The other, called Zenith, is testing it in advanced patients who are at elevated risk of death.

Those trials, along with long-term results from Winrevair’s other studies, will be necessary for physicians to understand the drug’s clinical profile, said Preston, of Tufts. “We need to learn more of the long-term effects.”