Winrevair (sotatercept) access landscape: PAH cost and coverage after ZENITH

Winrevair (sotatercept-csrk), FDA-approved in March 2024 and label-expanded on October 27, 2025 based on the phase 3 ZENITH trial (76 percent reduction in the composite of all-cause death, lung transplant, or PAH hospitalization vs placebo), is a medical-benefit, buy-and-bill specialty injectable billed under HCPCS J3590 (commercial) or C9399 (hospital outpatient) — there is no permanent product-specific J-code yet — with a ~$240,000/year list price that ICER pegged at roughly 7–13 times its $17,900–$35,400 cost-effective range, triggering an Access and Affordability Alert.

This article reviews the clinical, economic, and administrative access landscape for Winrevair, written for market-access directors, specialty pharmacy managers, and hospital billing coordinators. We examine how the drug's therapeutic mechanism translates into specific payer coverage policies, prior-authorization workflows, and buy-and-bill financial realities. For the general mechanisms of billing and coverage, see our primers on medical vs pharmacy benefit verification for specialty drugs and why buy-and-bill economics break in the first quarters after launch; for comparisons to other high-cost orphan drugs, see our analysis of how Casgevy access works under the CMS CGT model.

What is Winrevair and what did the ZENITH label expansion change?

Winrevair is a first-in-class activin signaling inhibitor. In Pulmonary Arterial Hypertension (PAH), the loss-of-function mutations in the bone morphogenetic protein receptor type II (BMPR2) pathway lead to an imbalance between growth-promoting activin/growth differentiation factor (GDF) signaling and growth-inhibiting BMP signaling. This imbalance results in the proliferation of endothelial and smooth muscle cells in the pulmonary vasculature, driving vascular remodeling, increased pulmonary vascular resistance, and eventually right-sided heart failure.

Unlike vasodilators (such as endothelin receptor antagonists, PDE5 inhibitors, and prostacyclin analogues) that target vasoconstrictive pathways, Winrevair is a fusion protein consisting of the extracellular domain of the human activin receptor type IIA linked to the Fc portion of human IgG1. By acting as a ligand trap, it binds to circulating activins (specifically activin A and activin B) and GDFs, restoring the balance between pro-remodeling and anti-remodeling pathways.

The drug's initial approval in March 2024 was supported by the STELLAR trial (N=323, WHO Functional Class II or III). In STELLAR, adding Winrevair to background PAH therapy increased the 6-minute walk distance (6MWD) by a placebo-adjusted 40.8 meters at week 24 and reduced the risk of clinical worsening or death by 84 percent.

On October 27, 2025, the FDA expanded the Winrevair labeling based on the phase 3 ZENITH trial (NCT04896008, N=172). ZENITH enrolled higher-risk, high-acuity PAH patients (WHO Functional Class III or IV at high risk of mortality) who were receiving triple background therapy (including an intravenous or subcutaneous prostacyclin). The trial demonstrated that Winrevair addition led to a 76 percent relative reduction in the composite endpoint of all-cause mortality, lung transplantation, or PAH-related hospitalization compared to placebo. This label expansion formally established Winrevair's role in the advanced, high-risk PAH segment, expanding the eligible population to patients previously considered candidates only for transplant or palliative care.

The Evolution of PAH Clinical Trial Endpoints

To contextualize the success of the STELLAR and ZENITH trials, it is valuable to examine the historical evolution of clinical trial endpoints in PAH. Historically, early trials in the 1990s and early 2000s were short-term studies (typically 12 to 16 weeks) that relied on surrogate hemodynamic endpoints — such as mean pulmonary artery pressure (mPAP), cardiac index, and pulmonary vascular resistance (PVR) — alongside the 6-minute walk distance. While these parameters demonstrated short-term vasoactive response, they did not necessarily correlate with long-term survival or disease progression.

A major milestone occurred with the SERAPHIN trial (evaluating macitentan) and the AMBITION trial (evaluating combination ambrisentan and tadalafil), which shifted the clinical standard toward long-term morbidity and mortality endpoints. These trials evaluated the time to first clinical worsening event, establishing a more rigorous framework for efficacy.

The Winrevair development program builds directly upon this historical progression. The STELLAR trial successfully targeted 6MWD as its primary endpoint but included time to clinical worsening as a key secondary measure. The ZENITH trial, by focusing on a composite endpoint of death, transplantation, or hospitalization in Class III/IV patients, has set a new benchmark for high-acuity intervention. For access teams, this clinical evidence justifies the drug's positioning at the top of the formulary, but it also provides payers with the evidence needed to mandate background vasodilator usage before Winrevair is initiated.

Comparing Winrevair to the Established PAH Class Landscape

To understand why Winrevair represents a paradigm shift, market access teams must position it against the existing therapeutic classes. While traditional agents focus on opening the constricted pulmonary vessels, Winrevair is the first agent that targets cellular proliferation and vascular remodeling directly. The table below details these differences:

This comparison highlights why Winrevair is viewed as an add-on therapy rather than a replacement. Vasodilators remain the primary therapy for acute hemodynamic management, while Winrevair is layered on top to halt the underlying proliferative remodeling. Consequently, payer prior-authorization criteria are structured to enforce this sequencing, requiring patients to remain on stable background vasodilator therapy before Winrevair is approved.

What does Winrevair cost, and how does that compare to ICER's benchmark?

The list price of Winrevair is approximately $14,000 per single-dose vial, which translates to an annual wholesale acquisition cost (WAC) of roughly $240,000 for a typical patient receiving a dose of 0.7 mg/kg subcutaneously once every 3 weeks.

This pricing strategy has drawn significant attention from health technology assessment (HTA) bodies. In its Final Evidence Report, the Institute for Clinical and Economic Review (ICER) calculated the health-benefit price benchmark (HBPB) for Winrevair to be between $17,900 and $35,400 per year. The HBPB represents the price range at which a drug's cost is aligned with its clinical benefit, using a threshold of $100,000 to $150,000 per quality-adjusted life year (QALY) gained. Winrevair's list price is 7 to 13 times higher than this value-based range:

The Canadian Agency for Drugs and Technologies in Health (CADTH) similarly noted that even under optimistic scenarios, the incremental cost-effectiveness ratio (ICER) for Winrevair in Canada was $436,796 per QALY compared to standard background therapy. CADTH's pharmacoeconomic review concluded that a price reduction on the order of 95 percent off the public list price would be required for sotatercept to approach a $50,000-per-QALY threshold, and it recommended reimbursement only conditional on a substantial, confidential price reduction.

Because the list price sits far above these benchmarks, payers have responded by placing Winrevair on the highest specialty formulary tiers, applying strict prior-authorization criteria to limit use to patients who match the trial populations.

How is Winrevair billed and under what HCPCS/NDC codes?

Winrevair is supplied in single-dose kits containing one 45 mg or one 60 mg vial. Because it is a provider-administered subcutaneous injection, it is processed under the medical benefit rather than the pharmacy benefit.

As of late 2025, CMS has not assigned a permanent, product-specific Healthcare Common Procedure Coding System (HCPCS) J-code for Winrevair. Providers must bill for the drug using unclassified or miscellaneous codes:

• HCPCS J3590: Unclassified biologics (used for commercial plans)
• HCPCS C9399: Unclassified drugs or biologicals (used for hospital outpatient departments under the Medicare Outpatient Prospective Payment System)
• HCPCS J3490: Unclassified drugs (alternative default code for specific regional payers)

The National Drug Codes (NDCs) for Winrevair kits are:

• NDC 0006-5090-01: 45 mg single-dose vial kit
• NDC 0006-5091-01: 60 mg single-dose vial kit
• NDC 0006-5068-01: Titration kit containing one 45 mg and one 60 mg vial (used for patients requiring a 105 mg dose)
• NDC 0006-5069-01: Maintenance kit containing two 60 mg vials (used for patients requiring a 120 mg dose)

Billing under miscellaneous codes like J3590 introduces significant administrative friction and financial risk. When a claim is submitted with J3590, the payer's adjudication system cannot automatically verify the drug or the price. The provider must submit the invoice showing the drug's name, NDC, administered dose, and acquisition cost alongside the claim form.

This requirement forces a manual review by the payer's claims department, which typically extends payment turnaround times from the standard 14 days for coded drugs to 60 or 90 days. During this period, the provider carries the $14,000-per-dose accounts receivable balance, exposing the clinic to significant cash flow pressure. This is a classic case of unclassified-code cash flow risk, where a delay in coding updates shifts the financial burden of launch biologics directly onto the provider.

Limited Distribution Networks (LDN) and Specialty Sourcing

Because of its high cost, temperature-control requirements, and clinical monitoring guidelines, Merck distributes Winrevair through a strict Limited Distribution Network (LDN). The drug cannot be sourced through standard retail pharmacies. Instead, only a select group of authorized specialty pharmacies (such as Accredo, CVS Specialty, and Caremark) are permitted to stock and dispense the medication.

For clinics operating under a buy-and-bill model, this LDN structure introduces several operational steps:

1. Prior-Authorization Approval: The clinic must secure clinical PA approval from the patient's payer before placing an order.
2. Authorized Distributor Sourcing: The clinic must purchase the vials from an authorized specialty distributor.
3. Cold-Chain Management: Winrevair must be stored under refrigeration (2°C to 8°C or 36°F to 46°F) and administered within specific stability windows once reconstituted.
4. Coordination with Specialty Pharmacies: If the payer mandates a specialty-pharmacy channel (preventing buy-and-bill), the clinic must coordinate with the authorized pharmacy to arrange delivery directly to the clinic ("clear-bagging" or "white-bagging"), ensuring the drug is present on the scheduled administration day.

This operational flow requires dedicated administrative staff to monitor shipments, verify prior-authorizations, and track inventory, increasing the overhead costs for clinics managing PAH patients.

What prior-authorization criteria do major payers require?

To manage the high cost of Winrevair, major US commercial and government payers have established strict prior-authorization (PA) protocols. While criteria vary slightly between plans (such as UnitedHealthcare, Blue Shield of California, Carelon, and the VA), they share a core set of clinical requirements:

Payer diagnostic requirements are highly specific. The VA Pharmacy Benefits Management criteria require the right-heart catheterization to be performed within the patient's medical history (not necessarily repeated at the time of the PA) to confirm mPAP >= 20 mmHg, pulmonary vascular resistance (PVR) >= 3 Wood units (or >= 240 dynes/sec/cm5), and pulmonary capillary wedge pressure (PCWP) <= 15 mmHg. This ensures the patient has true precapillary pulmonary hypertension and excludes Group 2 (left-heart disease) or Group 3 (lung disease) patients, who would not benefit from Winrevair.

Payers also enforce step-therapy or background-therapy rules. For example, UnitedHealthcare's policy requires the patient to have been on stable doses of a dual-combination regimen (an endothelin receptor antagonist like macitentan plus a PDE5 inhibitor like tadalafil) or a triple-therapy regimen for at least 30 days before Winrevair can be approved. Monotherapy use is excluded.

Reauthorization is typically granted for 12-month intervals. To secure renewal, the prescriber must submit clinical notes demonstrating that the patient has experienced a positive response, defined as an increase or stability in 6MWD, an improvement in WHO Functional Class, or a reduction in the frequency of PAH-related hospitalizations.

Prior-Authorization Intake Checklist for Clinic Teams

To minimize prior-authorization denials, clinic intake teams should compile the following documents before submitting the PA request to the payer:

• Right-Heart Catheterization (RHC) Report: Sourced from the patient's medical records to verify the precapillary hemodynamic parameters (mPAP, PVR, and PCWP).
• Baseline 6-Minute Walk Distance (6MWD) Assessment: Needed to establish a clinical benchmark for future reauthorization comparisons.
• Complete Blood Count (CBC): To verify baseline hemoglobin and platelet counts before initiating therapy.
• Current Medication Reconciliation: Documentation proving the patient is compliant with concurrent vasodilator background therapies (such as ERAs, PDE5is, or prostacyclins).
• Prescriber Specialty Credentials: Confirming the prescribing physician is a board-certified pulmonologist or cardiologist specialized in PAH management.

Is Winrevair on the medical or pharmacy benefit, and why does that matter?

Whether a specialty drug is covered under the medical or pharmacy benefit has major implications for patient out-of-pocket costs, provider operations, and channel management:

• Medical Benefit (Buy-and-Bill): In this model, the provider purchases Winrevair from a specialty distributor, stores it in their inventory, administers the injection to the patient, and bills the insurer for the drug and the administration. Under commercial plans, medical-benefit drugs are subject to coinsurance (often 20 percent), which can result in an out-of-pocket cost of $2,800 per dose for the patient until their maximum out-of-pocket limit is met. While Merck offers a copay card that reduces the patient's share to $0, these cards are not permitted for Medicare beneficiaries.
• Medicare Part B Exposure: Because Winrevair is provider-administered, Medicare covers it under Part B (medical benefit). Medicare Part B has a standard 20 percent coinsurance with no annual out-of-pocket maximum. For a Medicare beneficiary without supplemental insurance (Medigap), a single dose of Winrevair would result in a $2,800 out-of-pocket charge, and the annual exposure would exceed $48,000. This creates a significant affordability barrier for older patients, leading to high prior-authorization abandonment rates.
• Medicare Advantage and Prior Authorization: Under Medicare Advantage (Part C) plans, the prior-authorization process remains highly structured. While these plans must cover the same services as traditional Medicare, they frequently apply more restrictive clinical management guidelines, requiring extensive right-heart catheterization documentation and proof of failure on multiple background therapies before granting approval.
• Charitable Foundations and Patient Assistance: Due to the high out-of-pocket burden for Medicare beneficiaries, charitable foundations (such as the Patient Access Network [PAN] Foundation and the Patient Advocate Foundation) play a critical role in the access ecosystem. These disease-specific funds provide copay assistance grants to eligible Medicare patients. However, these funds are subject to periodic enrollment caps, meaning that a patient's access to therapy can be interrupted if foundation funding runs dry.
• Specialty Pharmacy (Brown-Bagging): To avoid the buy-and-bill financial risk and patient coinsurance issues, some clinics require the drug to be processed through the pharmacy benefit. In this scenario, a specialty pharmacy dispenses the drug and ships it directly to the clinic for administration (brown-bagging) or to the patient's home for self-administration. While this shifts the billing burden away from the clinic, it can introduce delivery delays, compromise cold-chain integrity, and complicate the provider's scheduling.

What adverse events drove the ZENITH safety profile?

While Winrevair represents an efficacy advance, its clinical trial safety profile requires active clinical monitoring and drives specific payer safety criteria:

• Erythrocytosis: Winrevair increases red blood cell counts by promoting erythropoiesis. In the ZENITH trial, increased hemoglobin occurred in 15.1 percent of patients in the Winrevair group. Prescribers must check hemoglobin and hematocrit levels before the first dose and before each subsequent dose for the first 5 doses, and periodically thereafter. Dosing must be delayed if hemoglobin rises above acceptable thresholds to prevent hyperviscosity and thromboembolic events.
• Thrombocytopenia: Conversely, Winrevair can cause severe drops in platelet counts. Platelet monitoring is required alongside hemoglobin. If a patient's platelet count drops below 50,000/mcL, the dose must be withheld until recovery.
• Epistaxis and Telangiectasia: Due to changes in vascular remodeling, epistaxis (nosebleeds) occurred in 45.3 percent of the Winrevair group in ZENITH, and telangiectasia (dilated small blood vessels on the skin or mucosal surfaces) was reported in 25.6 percent. These vascular changes are generally mild but represent a common, chronic class effect.
• Infections: Infections were the most commonly reported adverse-event category in the ZENITH safety profile, consistent with the broader sotatercept program. Most were upper respiratory tract infections, a pattern that reinforces the need for routine monitoring given the drug's modulation of transforming growth factor-beta (TGF-beta) superfamily signaling.

FAQ

Does Winrevair have a permanent HCPCS J-code?

No. As of late 2025, Winrevair does not have a permanent, product-specific HCPCS J-code. Providers must bill using miscellaneous or unclassified codes, such as J3590 for commercial plans, C9399 for Medicare hospital outpatient departments, or J3490. This unclassified status requires manual invoice submission and can delay provider reimbursement.

Why is Winrevair's price so far above ICER's range?

Merck priced Winrevair at $240,000 per year based on its status as a first-in-class biologic that offers a significant morbidity and mortality benefit (as demonstrated by the 76 percent reduction in composite endpoints in ZENITH). ICER's benchmark ($17,900–$35,400) is calculated from a de novo cost-effectiveness model designed to meet standard cost-per-QALY thresholds, creating a significant gap between the value-based price and the market price.

Can Winrevair be self-administered or must it be buy-and-bill?

The FDA label allows for self-administration by patients or caregivers after proper training. However, because of the requirement to monitor hemoglobin and platelets before each dose, many payers and clinics prefer the drug to be administered in a provider's office. This allows for lab draws and clinical assessment before injection.

Sources

• US FDA. Drugs@FDA database. Winrevair (sotatercept-csrk) initial BLA approval (March 26, 2024) and supplemental BLA approval for the expanded indication based on the ZENITH trial (s008, October 27, 2025). https://www.accessdata.fda.gov/scripts/cder/daf/
• Merck & Co. "U.S. FDA Approves Updated Indication for Winrevair (sotatercept-csrk) in Adults with Pulmonary Arterial Hypertension (PAH) based on Phase 3 ZENITH Study" (October 27, 2025) — clinical endpoint and trial design details. https://www.merck.com/news/u-s-fda-approves-updated-indication-for-winrevair-sotatercept-csrk-in-adults-with-pulmonary-arterial-hypertension-pah-who-group-1-pulmonary-hypertension-based-on-phase-3-zenith-study
• Institute for Clinical and Economic Review (ICER). "Pulmonary Arterial Hypertension: Final Evidence Report" (January 8, 2024) — cost-effectiveness models, list price analysis, and Health-Benefit Price Benchmark calculations. https://icer.org/assessment/pulmonary-arterial-hypertension-2023
• Blue Shield of California. "sotatercept-csrk (Winrevair) Medical Benefit Drug Policy" (Effective December 1, 2025) — unclassified coding, NDC listings, ICD-10 coverage codes, and clinical prior-authorization criteria. https://www.blueshieldca.com/content/dam/bsca/en/provider/docs/bsc-med-benefit-drug-policy/sotatercept-csrk-Winrevair-COMM-UMRx-provider.pdf
• Canadian Agency for Drugs and Technologies in Health (CADTH). "Sotatercept (Winrevair) Reimbursement Recommendation" (July 2024) — incremental cost-effectiveness ratio calculations and clinical criteria conditions. https://www.cda-amc.ca/sites/default/files/DRR/2024/SR0828REC-Winrevair.pdf