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PAH: The Era of Four-Pathway Therapy?

For years, pulmonary arterial hypertension treatment has focused on three pathways. Now there is a fourth—activin signaling—and the question is shifting from whether it belongs in the arsenal to how early we should use it.

For years, pulmonary arterial hypertension treatment has focused on three pathways:

• Nitric oxide–cGMP: PDE5 inhibitors or sGC stimulators

• Endothelin: endothelin receptor antagonists

• Prostacyclin: prostacyclin analogues or IP receptor agonists

Now there is a fourth: activin signaling, with sotatercept.

This is not simply another pulmonary vasodilator. Sotatercept targets abnormal signaling involved in pulmonary vascular proliferation and remodeling.

And the evidence is building:

• STELLAR: improved exercise capacity, hemodynamics, and measures of disease severity.

• ZENITH: reduced death, lung transplantation, or hospitalization for worsening PAH in high-risk patients—many already on triple therapy.

• HYPERION: reduced clinical worsening in recently diagnosed patients who remained intermediate or high risk despite background therapy.

The 2024 World Symposium on Pulmonary Hypertension treatment algorithm now recognizes these four therapeutic pathways and describes four-drug therapy as maximal medical therapy.

So perhaps the question is no longer whether PAH has a fourth therapeutic pathway. The question is how early should we use it?

Are we heading toward earlier four-pathway therapy for selected patients rather than waiting for failure of traditional triple therapy?

The PAH paradigm continues to evolve: nitric oxide + endothelin + prostacyclin + activin signaling.

Four pathways. Different mechanisms. One goal: prevent disease progression and protect the right ventricle.

Educational purposes only. Treatment decisions should be individualized.

#PulmonaryHypertension #PAH #Sotatercept #Winrevair #Cardiology #HeartFailure #RightHeartFailure

Pulmonary Arterial Hypertension (PAH): Four Pathways. A Brighter Tomorrow. Different mechanisms. A more complete approach. Four pathway cards joined by plus signs. 1. Nitric Oxide–cGMP Pathway — increase vasodilation and inhibit proliferation; drug class phosphodiesterase type 5 inhibitors (PDE5i) or soluble guanylate cyclase (sGC) stimulators; examples sildenafil, tadalafil, riociguat. 2. Endothelin Pathway — reduce vasoconstriction and proliferation; drug class endothelin receptor antagonists (ERA); examples bosentan, ambrisentan, macitentan. 3. Prostacyclin Pathway — increase vasodilation and inhibit proliferation; drug class prostacyclin analogues and IP receptor agonists; examples epoprostenol, treprostinil, iloprost, selexipag. 4. Activin Signaling Pathway — target vascular remodeling and proliferation; drug class activin signaling inhibitor; example sotatercept. What do the guidelines say: the 2022 ESC/ERS guidelines predated sotatercept and recommended risk-based escalation with combination therapy; the 2024 World Symposium on Pulmonary Hypertension (WSPH) treatment algorithm recognizes four therapeutic pathways and considers four-drug therapy as maximal medical therapy. Key question: how early should we introduce sotatercept — reserved for patients who remain intermediate or high risk despite traditional therapy, or considered earlier for selected patients? Bottom line: four pathways, complementary mechanisms; sotatercept adds a new approach by targeting the underlying biology of vascular remodeling; the goal is not just to improve symptoms but to prevent disease progression and protect the right ventricle; the right patient, at the right time.

Important notice

This content is for educational purposes only and is not medical advice for any individual patient. Patients should discuss diagnosis and treatment decisions with their own physician, or request a clinical consultation.

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