PDUFA Date

FDA reviews WINREVAIR label expansion off HYPERION's worsening-event data

Merck's sBLA rests on HYPERION's time-to-clinical-worsening result in newly diagnosed PAH, due September 21, 2026, even as the trial itself ended in Terminated status.

By AppliedXLJuly 13, 2026Trial NCT04811092

Executive Summary

Merck is asking FDA to expand WINREVAIR's label to newly diagnosed, first-line PAH patients, a earlier and larger population than its current approved use, with a decision due in September 2026.
The application rests on a completed Phase 3 trial that generated a full primary and secondary endpoint readout, including time-to-clinical-worsening and functional-capacity measures, before its registry status changed to terminated after results posted.
Because sotatercept is already approved in PAH, the question FDA must answer is whether the drug's known efficacy and safety profile reproduces in a newly diagnosed population, not whether the mechanism itself works.
Sotatercept remains the only activin-pathway therapy advanced to Phase 3 in PAH, so this decision has no direct in-class rival; the readthrough runs mainly to Merck's own extension studies of the same drug.

The application

Merck & Co., Inc. is seeking to update the U.S. product label for WINREVAIR based on the Phase 3 HYPERION trial (NCT04811092), which tested sotatercept plus background PAH therapy against placebo plus background therapy in newly diagnosed, intermediate- and high-risk PAH patients. FDA accepted the sBLA in February 2026 and set a PDUFA date of September 21, 2026. WINREVAIR is already approved for PAH; this filing would extend the drug's use earlier in the treatment sequence, to patients newly diagnosed rather than already on established therapy. NCT04811092+1

What HYPERION tested

HYPERION enrolled 321 patients across 13 countries, including the United States, Germany, France, and Brazil, and used median time to clinical worsening as its registered primary endpoint, defined as time from randomization to the first confirmed morbidity event or death from causes including hospitalization, atrial septostomy, lung transplant, or disease progression. Secondary endpoints included a multicomponent improvement measure combining six-minute walk distance, NT-proBNP, and WHO functional class at week 24, along with REVEAL Lite 2 and simplified French risk-score categories and overall survival. Results for these outcomes posted to ClinicalTrials.gov, giving FDA a completed dataset rather than a projected one. NCT04811092

The registry status question

HYPERION's timeline shows a trial that finished enrollment, reached a primary completion date of April 3, 2025, and moved to Completed status in May 2025 with 321 patients analyzed, down from an earlier enrollment target of 444. Results first posted on April 27, 2026, the same date the registry status changed from Completed to Terminated. That sequence, results posting concurrent with a status change to Terminated after the trial had already reached its primary completion date and reported enrollment, reads as a post-completion registry administrative closure rather than a trial that stopped before generating its endpoint data. NCT04811092

Safety signal from the completed dataset

The posted safety data show 39 of 160 sotatercept-arm patients at risk experienced a serious adverse event compared with 45 of 160 in the placebo arm, and 10 deaths in the sotatercept arm compared with 13 in the placebo arm, over a follow-up window of roughly 35 months. Commonly reported events across both arms included epistaxis, telangiectasia, and peripheral edema, consistent with the adverse-event pattern previously described for sotatercept in PAH. NCT04811092

Competitive and regulatory frame

Sotatercept has no direct in-class rival that has advanced to Phase 3 in PAH targeting Activin A: the nearest comparator sharing target and modality is a Phase 4 University of Alberta study of sotatercept itself, and the broader PAH field is populated by mechanistically distinct small-molecule programs such as seralutinib, ralinepag, and treprostinil palmitil, none of which share sotatercept's activin-pathway mechanism. No Priority Review, Breakthrough Therapy, or other designation events are on record for this submission, leaving a standard review track as the operative assumption for the September date.

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