Is Sotatercept indicated for Group 3 pulmonary hypertension (PH)?

Sotatercept is NOT indicated for Group 3 pulmonary hypertension

Sotatercept (WINREVAIR) is FDA-approved exclusively for WHO Group 1 pulmonary arterial hypertension (PAH) in adults with functional class II or III symptoms on background therapy—it has no role in Group 3 PH due to lung disease and/or hypoxemia. 1

Why Sotatercept Does Not Work in Group 3 PH

Mechanism Mismatch

Sotatercept is an activin signaling inhibitor that rebalances pro-proliferative (ActRIIA/Smad2/3) and anti-proliferative (BMPRII/Smad1/5/8) pathways to reverse pulmonary vascular remodeling 1. This mechanism targets the proliferative arteriopathy characteristic of PAH (Group 1), not the hypoxic vasoconstriction and parenchymal destruction that drive Group 3 PH.

The Core Problem with Group 3 PH

Group 3 PH arises from underlying lung disease (COPD, interstitial lung disease, bronchopulmonary dysplasia) where the primary pathology is in the lung parenchyma, not the pulmonary vasculature 2. The PH is typically mild-to-moderate and secondary to:

• Chronic hypoxemia
• Loss of vascular bed from parenchymal destruction
• Hypoxic pulmonary vasoconstriction
• Ventilation-perfusion (V/Q) mismatch

Evidence Against PAH-Targeted Therapies in Group 3

Current guidelines explicitly state there is no specific therapy for Group 3 PH apart from optimal management of the underlying lung disease 3. The 2015 ESC/ERS guidelines note that PAH-approved therapies are not recommended in Group 3 PH 4. The 2020 Canadian guidelines emphasize that "published experience with PAH-targeted drugs is scarce, and there is no evidence for improved clinical outcomes with these drugs in patients with group III PH" 3.

The V/Q Mismatch Risk

A critical concern with pulmonary vasodilators in Group 3 PH is worsening V/Q matching, which can paradoxically worsen hypoxemia 2, 3. While sildenafil is sometimes used cautiously in specific Group 3 contexts (e.g., BPD in infants), this is done with careful monitoring and represents off-label use in selected cases 2.

What TO Do for Group 3 PH

The foundation of Group 3 PH management is treating the underlying lung disease 2:

1. Optimize the primary lung condition

   • Bronchodilators and anti-inflammatory therapy for COPD
   • Antifibrotic agents for interstitial lung disease
   • CPAP/BiPAP for sleep-disordered breathing

2. Normalize oxygenation and ventilation

   • Supplemental oxygen to maintain SpO2 >90-92%
   • Avoid atelectasis
   • Minimize further lung insults

3. Screen for alternative causes if PH is severe

   • If PH appears "out of proportion" to mild lung disease, consider:
     • Left heart disease (Group 2)
     • CTEPH (Group 4)
     • Coexisting PAH (Group 1)
   • Severe PH/RV failure is unlikely from mild lung disease alone 3

4. Lung transplantation

   • For progressive Group 3 PH despite optimal therapy
   • Outcomes are less favorable than Group 1 PH 2

Common Pitfall to Avoid

Do not extrapolate sotatercept's success in PAH to Group 3 PH. The disease mechanisms are fundamentally different. While sotatercept dramatically improves hemodynamics and exercise capacity in PAH patients 5, 6, 7, these benefits stem from reversing proliferative vascular remodeling—a process that is not the primary driver of Group 3 PH. Using sotatercept off-label in Group 3 would be:

• Unsupported by evidence
• Potentially harmful (risk of worsening V/Q mismatch)
• Expensive without proven benefit
• Outside FDA-approved indications 1