Winrevair - Drug Monograph

Introduction

Winrevair (sotatercept) is a first-in-class activin receptor type IIA-Fc (ActRIIA-Fc) fusion protein approved for the treatment of pulmonary arterial hypertension (PAH). It represents a paradigm shift in PAH therapy by targeting the underlying proliferative vascular remodeling rather than relying solely on vasodilation. Its clinical relevance lies in its ability to improve exercise capacity and reduce the risk of clinical worsening events in patients with WHO Functional Class II–III PAH.

Drug Class and Overview

• Class: Activin signaling inhibitor; a recombinant fusion protein comprising the extracellular domain of human activin receptor type IIA linked to the Fc domain of human IgG1.
• Related agents: No direct pharmacologic analogs are currently approved; it is distinct from endothelin receptor antagonists (ERAs), phosphodiesterase-5 inhibitors (PDE5is), soluble guanylate cyclase stimulators, and prostacyclin pathway agents.
• Key distinguishing feature: Unlike conventional PAH therapies that primarily cause pulmonary vasodilation, sotatercept directly targets the imbalance between pro- and anti-proliferative TGF-β superfamily signaling, thereby reducing vascular remodeling.

Mechanism of Action

Sotatercept acts as a ligand trap for members of the TGF-β superfamily, particularly activin A, activin B, and growth differentiation factor 11 (GDF-11). By binding these ligands, it prevents their interaction with membrane-bound ActRIIA and ActRIIB receptors. In PAH, overactivation of activin signaling promotes pulmonary vascular smooth muscle cell proliferation, endothelial dysfunction, and intimal fibrosis. By sequestering these ligands, sotatercept restores the balance toward the anti-proliferative bone morphogenetic protein (BMP) signaling pathway, leading to reduced vascular remodeling, decreased pulmonary vascular resistance, and improved right ventricular function.

Indications

• Approved indication: Treatment of pulmonary arterial hypertension (PAH) (WHO Group 1) in adult patients with WHO Functional Class II–III, to improve exercise capacity and reduce the risk of clinical worsening events.
• Use in combination: Approved for use as monotherapy or in combination with background PAH therapy (e.g., ERAs, PDE5is, prostacyclin analogs).
• Not indicated for pulmonary hypertension due to other etiologies (e.g., WHO Group 2–5).

Dosage and Administration

• Route: Subcutaneous (SC) injection only.
• Initial dosing: 0.3 mg/kg administered subcutaneously every 3 weeks.
• Dose titration: Increase to 0.7 mg/kg every 3 weeks if hemoglobin (Hgb) is ≥ 15 g/dL (or ≥ 14 g/dL in females) and platelet count is ≥ 100,000/µL.
• Maximum dose: 0.7 mg/kg every 3 weeks.
• Dose adjustments:
• Hemoglobin increase: If Hgb increases by > 1 g/dL from baseline, do not escalate the dose. If Hgb exceeds 18 g/dL (or 17 g/dL in females), hold therapy until Hgb returns to ≤ 17 g/dL (or ≤ 16 g/dL in females), then resume at a reduced dose.
• Thrombocytopenia: If platelet count falls below 50,000/µL, hold therapy until recovery, then resume at a reduced dose.
• Renal/hepatic impairment: No specific dose adjustments are established; use with caution in severe impairment (limited data).
• Pediatric/geriatric: Safety and efficacy in pediatric patients have not been established. No specific geriatric dose adjustments are recommended, though older patients may have higher bleeding risk.

Pharmacokinetics

• Absorption: Subcutaneous administration yields a bioavailability of approximately 85%; peak concentrations are reached in about 7–14 days.
• Distribution: Large protein therapeutic; primarily confined to the vascular and interstitial spaces. Volume of distribution is approximately 7 L.
• Metabolism: Degraded via general protein catabolism into small peptides and amino acids; not metabolized by CYP450 enzymes.
• Elimination: Clearance is approximately 0.35 L/day; terminal half-life is approximately 20–30 days, supporting every-3-week dosing.
• Special populations: Body weight significantly affects exposure; weight-based dosing is used. No clinically meaningful differences in exposure based on age, sex, or mild-to-moderate renal/hepatic impairment.

Contraindications

• Pregnancy: Sotatercept is contraindicated in pregnant women due to embryofetal toxicity, including teratogenicity and fetal loss, based on animal studies.
• Hypersensitivity: Known hypersensitivity to sotatercept or any of its excipients.

Warnings and Precautions

• Embryofetal toxicity: Can cause fetal harm. Verify pregnancy status in females of reproductive potential prior to initiation. Advise use of effective contraception during treatment and for at least 4 months after the last dose.
• Hemoglobin increase: Sotatercept can cause excessive erythrocytosis. Monitor Hgb before each dose and for the first 5 doses, then periodically. Severe erythrocytosis increases the risk of thromboembolic events and hyperviscosity syndrome.
• Thrombocytopenia: Dose-dependent decreases in platelet count can occur. Monitor platelets before each dose and for the first 5 doses, then periodically. Severe thrombocytopenia increases bleeding risk.
• Bleeding risk: Sotatercept may increase the risk of bleeding, particularly in patients on anticoagulation or antiplatelet therapy. Monitor for signs of bleeding.
• Hypotension: Can cause hypotension, especially when added to background vasodilator therapy. Monitor blood pressure and adjust concomitant antihypertensive therapy as needed.
• Infection risk: As an immunomodulatory agent, there is a theoretical risk of increased infection; no significant increase in infections was observed in clinical trials.

Drug Interactions

• Anticoagulants/Antiplatelets: Concomitant use increases the risk of bleeding. Monitor for signs of bleeding and adjust therapy as clinically indicated.
• Antihypertensives: Additive hypotensive effects may occur. Monitor blood pressure and adjust doses of antihypertensive agents as needed.
• Hormonal contraceptives: No direct pharmacokinetic interaction is expected; however, because sotatercept may cause fetal harm, use of reliable non-hormonal or hormonal contraception is recommended in females of reproductive potential.
• CYP450 substrates: No clinically significant CYP450-mediated interactions are expected, as sotatercept is a biologic agent not metabolized by CYP enzymes.

Adverse Effects

• Common (≥ 10%):
• Headache
• Epistaxis
• Dizziness
• Diarrhea
• Nausea
• Palpitations
• Erythrocytosis (elevated Hgb)
• Thrombocytopenia
• Serious/rare:
• Thromboembolic events (related to erythrocytosis)
• Severe bleeding (related to thrombocytopenia)
• Hypotension
• Hypersensitivity reactions (including rash and urticaria)
• Fetal harm (teratogenicity)

Monitoring Parameters

• Hemoglobin: Check before each dose for the first 5 doses, then periodically (e.g., every 3–6 months) or as clinically indicated.
• Platelet count: Check before each dose for the first 5 doses, then periodically.
• Pregnancy status: Verify in females of reproductive potential prior to initiation and periodically during treatment.
• Blood pressure: Monitor at each visit, especially when initiating or titrating concomitant antihypertensive therapy.
• Clinical status: Assess WHO Functional Class, exercise capacity (e.g., 6-minute walk distance), and signs of right heart failure at each visit.
• Bleeding signs: Monitor for epistaxis, bruising, or other bleeding symptoms, particularly in patients on anticoagulants.

Patient Education

• Administration: Winrevair is given as a subcutaneous injection every 3 weeks, typically by a healthcare provider. Do not self-administer unless trained.
• Pregnancy prevention: Use effective contraception during treatment and for at least 4 months after the last dose. Notify your provider immediately if you become pregnant or plan to become pregnant.
• Bleeding precautions: Report any unusual bruising, bleeding from the gums, nosebleeds, or blood in stool/urine.
• Blood tests: You will need regular blood tests to monitor your red blood cell and platelet counts before each dose.
• Dizziness/low blood pressure: Rise slowly from sitting or lying positions. Report persistent dizziness or fainting.
• Missed dose: If a dose is missed, contact your healthcare provider to reschedule as soon as possible; do not double the dose.

Clinical Pearls

1. First-in-class therapy: Sotatercept is the first approved agent that directly targets the underlying vascular remodeling in PAH, rather than just promoting vasodilation.
2. Dose titration is Hgb-driven: Dose escalation to 0.7 mg/kg is only permitted if hemoglobin and platelet thresholds are met; this minimizes the risk of erythrocytosis and thrombocytopenia.
3. Add-on therapy: In clinical practice, sotatercept is most commonly added to background PAH therapy (e.g., ERA + PDE5i) in patients who remain symptomatic, rather than used as first-line monotherapy.
4. Not for all PH groups: It is specifically indicated for WHO Group 1 PAH; it should not be used for pulmonary hypertension due to left heart disease, lung disease, or chronic thromboembolic disease.
5. Monitoring is essential: The most clinically significant adverse effects—erythrocytosis and thrombocytopenia—are manageable with regular monitoring and dose adjustments.
6. Pregnancy contraindication: Given the teratogenic potential, pregnancy testing and contraception counseling are mandatory before and during therapy.

References

1. U.S. Food and Drug Administration. Winrevair (sotatercept) Prescribing Information. 2024. https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/761338s000lbl.pdf
2. Humbert M, McLaughlin V, Gibbs JSR, et al. Sotatercept for the treatment of pulmonary arterial hypertension. N Engl J Med. 2021;384(13):1204-1215.
3. Hoeper MM, Badesch DB, Ghofrani HA, et al. Phase 3 trial of sotatercept for treatment of pulmonary arterial hypertension. N Engl J Med. 2023;388(16):1478-1490.
4. Galiè N, Humbert M, Vachiery JL, et al. 2015 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension. Eur Heart J. 2016;37(1):67-119.
5. Ruopp NF, Cockrill BA. Diagnosis and treatment of pulmonary arterial hypertension: a review. JAMA. 2022;327(14):1379-1391.
6. Yndestad A, Larsen KO, Øie E, et al. Role of activin A in pulmonary arterial hypertension. Am J Respir Crit Care Med. 2009;180(5):448-456.
7. Brunton LL, Hilal-Dandan R, Knollmann BC. Goodman & Gilman's The Pharmacological Basis of Therapeutics. 13th ed. McGraw-Hill; 2018.
8. Katzung BG, Vanderah TW. Basic and Clinical Pharmacology. 15th ed. McGraw-Hill; 2021.
9. Lexicomp Online. Sotatercept: Drug Information. Wolters Kluwer; 2024.