Sotatercept Versus an Untried Prostacyclin Route in Escalating PAH
Dana has already tried — and refused to repeat — one prostacyclin delivery route for her escalating PAH. Whether that counts as the pathway failing, or only one route within it, decides whether sotatercept or an untried oral agent comes next.
Dana R., a 52-year-old woman, has run a small embroidery-and-monogramming shop out of her garage for the better part of a decade — steady, seated work she chose deliberately three years ago, after a diagnosis of idiopathic pulmonary arterial hypertension made the standing, lifting, and stair-climbing of her previous job as a florist's assistant impossible to sustain. Apart from the PAH itself she has no other chronic disease — no diabetes, no hypertension — and takes no medication beyond her PAH regimen. She has been on ambrisentan and tadalafil, the guideline dual combination, since diagnosis, and for the first eighteen months her six-minute walk distance and functional class held reasonably steady. Over the past four months that has reversed: she is now Functional Class III, her 6MWT distance has fallen from 410 to 340 meters, and a repeat right heart catheterization last week showed a cardiac index of 2.1 L/min/m² and a pulmonary vascular resistance of 9.0 Wood units — both worse than her post-diagnosis baseline, the kind of hemodynamic drift that by itself argues for escalating therapy rather than watching further.
Standard escalation from dual oral therapy is a parenteral or inhaled prostacyclin, and two years ago she tried exactly that: a subcutaneous treprostinil trial she stopped after eleven days, the infusion-site pain severe enough that she was taking gabapentin and still not sleeping, unwilling to repeat the experience even with a different delivery route offered. That refusal is where today's discussion actually starts. Sotatercept, an activin-signaling inhibitor rather than a vasodilator, improved six-minute walk distance and pulmonary vascular resistance in STELLAR (Hoeper and colleagues, 2023) when added to background therapy in symptomatic patients split almost evenly between Functional Class II and III. The team keeps describing that population as though it were Dana's, and it is worth checking rather than assuming: 61.3% of STELLAR's participants were on triple therapy and 39.9% were receiving prostacyclin infusion at enrollment. Dana is on two oral drugs and has refused the infusion. The typical STELLAR patient had therefore already completed the escalation step she declined — meaning the trial does not show what sotatercept does instead of a prostacyclin, it shows what sotatercept does after one, in a population that had generally tolerated what she could not.
Clinic follow-up, six weeks after the repeat catheterization
Dana already told us what a prostacyclin trial costs her — eleven days of infusion-site pain bad enough to need gabapentin, and she was clear afterward she wouldn't try it again in any parenteral form. STELLAR showed real improvement in pulmonary vascular resistance and six-minute walk distance on top of background therapy in symptomatic patients, and her hemodynamics are drifting in exactly the direction that trial reversed. Asking her to attempt a prostacyclin a second time isn't a neutral ask; refusal and nonadherence are real risks of their own, and a drug she will actually take beats one she's already told us she won't.
You're right that her subcutaneous trial was genuinely traumatic, not exaggerated — but what failed was the route, not necessarily the pathway. She's never been offered an oral or inhaled formulation.
Calling this "prostacyclin refused" when only one of three delivery routes has actually been tried treats a route failure as a class failure. And the STELLAR comparison doesn't support the substitution as cleanly as it sounds: 61.3% of that trial's patients were on triple therapy and 39.9% were on prostacyclin infusion. Its typical participant had already been through the escalation Dana refused and tolerated it. So STELLAR tells us what sotatercept adds after a prostacyclin, not what it does in place of one — which is the question we're actually being asked today.
Both of you are arguing past the same fact — she has genuine, documented intolerance on one axis of escalation, and there's a route she hasn't tried. Oral treprostinil doesn't carry the infusion-site pain that ended her subcutaneous trial; its own dose-limiting effects — headache, jaw pain, gastrointestinal upset — arise from a different mechanism entirely, systemic prostacyclin-receptor activity rather than local tissue irritation. This isn't the same drug in a different bottle. Try that first, with a defined short interval before reassessing, rather than deciding today that the entire prostacyclin pathway is closed to her, or that sotatercept is being reached for ahead of an option she hasn't actually failed.
Agreed: start oral treprostinil today, with formal reassessment — repeat right heart catheterization and 6MWT — at twelve weeks rather than the longer interval used for a stable patient.
Not agreed: what comes next if oral treprostinil also proves poorly tolerated, rather than simply ineffective. The pulmonary hypertension specialist would move to sotatercept at that point, given Dana's cumulative history across the prostacyclin class; the cardiologist would want one further within-class attempt — inhaled treprostinil — before conceding the pathway itself has failed her. Neither position was resolved; both agreed to revisit it only if oral treprostinil doesn't hold up.