A key unmet need in pulmonary arterial hypertension (PAH ) is a lack of disease-modifying, curative therapies. This may soon change, following Merck ’s announcement on 10 October of positive top-line results from its Phase III STELLAR trial (NCT04576988) evaluating sotatercept in patients with PAH. In interviews with GlobalData, key opinion leaders (KOLs) have expressed excitement surrounding the potential of sotatercept to revolutionise the PAH space.

Originally developed by Acceleron Pharma , sotatercept is the only drug to have achieved breakthrough therapy designation in the US for PAH, alongside orphan designation in the US and the EU. Merck acquired Acceleron Pharma and its pipeline therapies in September 2021 for $11.5 billion, with sotatercept being the key drug. KOLs believe that this acquisition has paid off for Merck and have positioned it as a top competitor, with the potential to overtake the current leader in the PAH space, United Therapeutics . One KOL notes: “I think it will be a home run for Merck and […] will recoup most of the $12 billion they invested in the product.”

Nonetheless, sotatercept will face hurdles upon launch. Notably, the initial five doses of sotatercept, administered subcutaneously every 21 days, require specialty infrastructure lacking in community centres. One KOL stated: “The hurdle to this is going to be how it’s rolled out […] I think, outside of the big academic centres and big pulmonary hypertension practices, there won’t be a lot of uptake.” KOLs also highlighted the possibility of non-responders and issues with tolerance. A KOL commented: “I would expect even with sotatercept, that we have responders and non-responders. It may work in the beginning but not in the long term.” Follow-up studies evaluating the long-term safety and efficacy of sotatercept are currently underway.

Despite these hurdles, KOLs interviewed by GlobalData have reported they expect sotatercept to become a leading therapy in the PAH market due to strong efficacy and clinical data, and as the first disease-modifying therapy, a significant breakthrough for PAH patients. Sotatercept is forecast to launch in 2024 in the US, and 2025 in the rest of the world. GlobalData predicts sotatercept to gain a large market share and dominate other pipeline disease-modifying therapies such as ralinepag and imatinib.