Sotatercept at Diagnosis or After Standard Therapy in High-Risk PAH
Diagnosed today at the highest risk tier PAH offers, Marcus's team must decide whether sotatercept belongs in his very first regimen or whether he first needs the background therapy every sotatercept trial assumed patients already had.
Marcus T., a 39-year-old man, teaches high school wood shop and had spent months quietly working around a breathlessness he assumed was simply being out of shape — until three weeks ago, when he fainted demonstrating a table saw cut and a colleague called an ambulance rather than let him walk it off. The syncope led to an echocardiogram, then a right heart catheterization that confirmed idiopathic pulmonary arterial hypertension: mean pulmonary artery pressure 52mmHg, pulmonary vascular resistance 11.0 Wood units, cardiac index 1.9 L/min/m², right atrial pressure 14mmHg — a hemodynamic picture that lands him, by REVEAL Lite 2 scoring, in the high-risk tier at the moment of diagnosis, not after treatment has had a chance to fail. His NT-proBNP returned at 1,850 pg/mL, which on its own carries the maximum adverse weighting that score assigns any single variable. He has no other cardiopulmonary disease, no connective tissue disease on serologic workup, and until three weeks ago no medications at all.
The question in front of the team isn't whether to treat aggressively — that part is settled by his risk tier alone — it's whether sotatercept belongs in the initial regimen or waits. The evidence here is not thin, which is what makes the decision awkward. Sotatercept now has three positive phase 3 trials, and one of them reaches his exact risk stratum: ZENITH (Humbert and colleagues, 2025) enrolled WHO Functional Class III and IV patients at high risk of mortality and was stopped early for efficacy, with a first morbidity-or-mortality event in 17.4% on sotatercept against 54.7% on placebo. HYPERION (McLaughlin and colleagues, 2025) went earlier still, enrolling patients within a year of diagnosis, and reported clinical worsening in 10.6% versus 36.9%. What every one of the three shares is the enrollment condition Marcus does not meet: STELLAR required stable background therapy, ZENITH required maximum tolerated double or triple therapy, and HYPERION required stable double or triple therapy for at least 90 days before screening, in patients averaging 7.2 months from diagnosis. Marcus is on day three, holding a single dose of sildenafil started in the emergency department — 87 days short of that floor, and short of the double-or-triple regimen the floor is measured against. His risk tier puts him inside the population these trials were built for; his treatment history puts him outside every one of them, and it is the treatment history, not the risk tier, that the team has any power to change this week.
Inpatient pulmonary hypertension consult, hospital day 3
His REVEAL Lite 2 score puts him in the high-risk tier before we've given any therapy a chance to work, and high-risk status at diagnosis is one of the strongest predictors we have of early mortality in this disease. We already treat high-risk patients aggressively from day one — that's why parenteral prostacyclin is standard initial therapy at this tier, not something reserved for treatment failure. And we are no longer guessing about sotatercept in patients this sick: ZENITH randomized exactly this stratum, Functional Class III and IV at high risk of mortality, and the data monitoring committee stopped it early because the separation was so large — a first death, transplant, or PAH hospitalization in 17.4% on drug against 54.7% on placebo. That is not a signal I want to withhold from a 39-year-old with a cardiac index of 1.9 while we wait to see whether three other drugs move him.
You're right about ZENITH's magnitude, and I'd add HYPERION to your side of the ledger while we're at it — it enrolled inside the first year after diagnosis and still cut clinical worsening from 36.9% to 10.6%. So I'm not going to argue the drug doesn't work early. I'm going to argue about the word "initial."
Read ZENITH's own entry criterion back to me: maximum tolerated background therapy, double or triple, in every single participant. HYPERION's was stable double or triple therapy for at least 90 days before screening, and its patients averaged 7.2 months out from diagnosis. Marcus is on day three with one drug. Every trial you and I both want to cite added sotatercept to a regimen that had already been built and pushed to its ceiling — not one of them tested it as the thing you reach for instead of building that regimen. "Sotatercept helps high-risk patients" is established. "Sotatercept helps high-risk patients who have never been given a second agent" has never been asked, and answering it by assumption in a man whose right atrial pressure is already 14 is not the same as answering it.
Then build the regimen the trials assumed he already had, and build it fast. Start what the risk tier calls for — a prostacyclin-pathway agent alongside his oral therapy — and understand that as constructing HYPERION's entry criteria rather than as postponing sotatercept. That reframing has a practical consequence you're both circling: HYPERION's 90-day stability requirement is the interval, and it is also roughly the interval at which we would want repeat hemodynamics in a man this sick anyway. Reassess at ten to twelve weeks rather than the three-to-six-month window we'd use in a lower-risk patient, and if he is still high-risk then, he is no longer a patient sotatercept has never been studied in — he is a HYPERION patient, and we add it on the evidence rather than ahead of it. The one thing I would not do is let "treat aggressively" and "treat with the newest agent" collapse into the same sentence. His cardiac index of 1.9 argues for speed. It does not, by itself, argue for which drug.
Agreed: start standard high-risk-tier initial combination therapy — inhaled treprostinil, sildenafil, and ambrisentan — with formal reassessment at 10-12 weeks rather than the longer interval used for lower-risk patients.
Not agreed: whether the background-therapy requirement common to all three sotatercept trials is a real precondition for the drug's effect or an artifact of how the trials were built. The pulmonary hypertension specialist reads it as the latter — a recruitment and regulatory convenience the field will abandon once someone runs the trial — and would have started sotatercept today. The cardiologist declines to convert an unasked question into an answered one, noting that ZENITH's participants were on maximum tolerated therapy precisely because the effect was measured on top of it. Both accepted that Marcus's ten-to-twelve-week reassessment settles his own case without settling theirs.