Last updated: September 7, 2026
Nucala, GSK’s anti-interleukin-5 biologic mepolizumab, has developed from a severe eosinophilic asthma product into a multi-indication respiratory and immunology franchise. Global sales increased from approximately £1.1 billion in 2021 to about £1.7 billion in 2023. Growth has been driven by chronic rhinosinusitis with nasal polyps, hypereosinophilic syndrome, eosinophilic granulomatosis with polyangiitis and broader penetration in severe asthma.
U.S. biologic exclusivity is scheduled to expire in November 2027, subject to any applicable pediatric extension. Patent protection is more fragmented. Core antibody patents are approaching or have reached their primary term, while formulation, manufacturing, dosing and indication patents may extend commercial protection into the 2030s. No Nucala biosimilar had received FDA approval through the available public record.
What is Nucala and how does mepolizumab work?
Nucala is a monoclonal antibody that binds interleukin-5, or IL-5. IL-5 regulates the growth, activation and survival of eosinophils, inflammatory cells implicated in severe eosinophilic asthma and several eosinophil-driven disorders.
| Attribute |
Nucala |
| Active ingredient |
Mepolizumab |
| Manufacturer |
GSK |
| Biologic class |
Humanized anti-IL-5 monoclonal antibody |
| U.S. regulatory application |
BLA 125526 |
| Initial FDA approval |
November 4, 2015 |
| Principal delivery |
Subcutaneous injection |
| Initial indication |
Severe eosinophilic asthma |
| Key later indications |
EGPA, hypereosinophilic syndrome and CRSwNP |
| Main competitors |
Fasenra, Dupixent, Cinqair and Tezspire |
| Primary commercial markets |
United States, Europe and Japan |
Nucala reduces eosinophil counts rather than directly bronchodilating the airway. Its commercial value therefore depends on biomarker-defined patient selection, specialist prescribing and the ability to reduce oral corticosteroid use, exacerbations and hospital utilization.
What FDA indications does Nucala have?
Nucala has the broadest eosinophil-focused indication set among GSK’s respiratory biologics.
FDA-approved indications and milestones
| Indication |
FDA milestone |
Commercial relevance |
| Severe eosinophilic asthma |
November 2015 |
Original and largest indication |
| Pediatric severe eosinophilic asthma |
September 2019 expansion to younger patients |
Expanded eligible population |
| Hypereosinophilic syndrome |
September 2020 |
Rare-disease and orphan-market revenue |
| Chronic rhinosinusitis with nasal polyps |
October 2021 |
Added ENT and allergy prescribers |
| Eosinophilic granulomatosis with polyangiitis |
December 2021 |
Rare autoimmune indication |
The asthma label generally requires an eosinophilic phenotype and use as an add-on maintenance therapy. Nucala is not a rescue medicine and does not replace inhaled corticosteroids or acute treatment.
The CRSwNP indication expanded the addressable population beyond patients whose primary diagnosis is asthma. EGPA and hypereosinophilic syndrome provide smaller patient pools but can support higher treatment persistence and lower direct competition.
When does Nucala lose FDA biologic exclusivity?
Nucala’s 12-year reference-product exclusivity period is expected to end on November 4, 2027, based on the first U.S. licensure date. The Biologics Price Competition and Innovation Act prevents FDA approval of a biosimilar referencing Nucala before that date, regardless of the remaining patent term. FDA regulatory exclusivity and patent protection are separate rights. [1]
A six-month pediatric extension could move the effective regulatory barrier to approximately May 2028 if GSK qualified for and obtained pediatric exclusivity. Public commercial forecasts generally use 2027-2028 as the first meaningful U.S. biosimilar-entry window.
Orphan exclusivity for individual rare-disease indications does not automatically block a biosimilar across all Nucala indications. It can restrict approval of the same biologic for the protected orphan indication during the applicable seven-year period. The practical effect depends on the reference-product label, the biosimilar sponsor’s proposed indications and FDA’s orphan-drug rules.
What patents protect Nucala?
Nucala’s protection is based on a portfolio rather than a single blocking patent. The relevant categories include:
- Anti-IL-5 antibody composition patents.
- Pharmaceutical composition and formulation patents.
- Dosing and administration patents.
- Method-of-use patents for eosinophilic diseases.
- Manufacturing and cell-line process patents.
- Patents covering specific patient populations or biomarker-defined treatment.
The earliest anti-IL-5 antibody filings have priority dates more than two decades old. Their ordinary 20-year terms are therefore largely exhausted or near exhaustion. Later continuation, formulation and use patents can create additional litigation issues, but they are less likely to provide the same breadth as a valid composition patent.
How strong is the Nucala patent estate?
The Nucala estate is commercially meaningful but less structurally robust than a product protected by a late-expiring composition-of-matter patent. Its main strengths are:
- A long clinical and regulatory record.
- Multiple approved indications.
- Complex biologic manufacturing.
- A large installed prescriber and patient base.
- Potential patent coverage around dosing, formulations and indications.
Its weaknesses are:
- The original antibody discovery period is old.
- Biosimilar competition can proceed after regulatory exclusivity even if some use patents remain.
- A biosimilar may seek a narrower label and omit patented indications.
- Patent litigation may not prevent substitution for unprotected uses.
- Physician familiarity with competing IL-5 and IL-5-receptor products limits pricing power.
A current patent-by-patent legal conclusion requires the operative FDA Purple Book patent disclosures, USPTO prosecution records and any later-filed continuation patents. The Orange Book is not the primary listing system for Nucala because Nucala is a biologic, not a conventional small-molecule drug. [2]
What is the Orange Book and Purple Book status of Nucala?
Nucala is not assessed through the conventional Orange Book framework used for approved small-molecule drugs. Its reference-product and biosimilar status are tracked through FDA biologics systems, including the Purple Book.
| Regulatory issue |
Nucala position |
| Orange Book listing |
Not the controlling biologic-patent mechanism |
| Reference biologic |
Yes |
| BLA |
125526 |
| Biosimilar pathway |
Section 351(k) of the Public Health Service Act |
| Reference-product exclusivity |
12 years from first licensure |
| Interchangeability |
No FDA-approved interchangeable biosimilar publicly identified through the available record |
| Paragraph IV challenge |
Not applicable in the same form as an ANDA challenge |
| Patent-resolution framework |
BPCIA “patent dance” and related litigation |
Biosimilar applicants can raise patent disputes under the BPCIA and may litigate before launch. A sponsor can also pursue a limited indication strategy, potentially avoiding method-of-use patents covering particular Nucala uses.
Which companies compete with Nucala?
Nucala competes in a crowded severe asthma and type-2 inflammation market.
| Product |
Company |
Target or mechanism |
Competitive position |
| Nucala |
GSK |
IL-5 |
Established eosinophil-focused franchise |
| Fasenra |
AstraZeneca |
IL-5 receptor alpha |
Eosinophil depletion and less frequent maintenance dosing |
| Dupixent |
Sanofi/Regeneron |
IL-4 receptor alpha |
Broad type-2 inflammation franchise, including asthma and CRSwNP |
| Cinqair |
Teva |
IL-5 |
Intravenous administration limits convenience |
| Tezspire |
Amgen/AstraZeneca |
TSLP |
Broad severe-asthma positioning, less dependent on eosinophil count |
| Xolair |
Genentech/Novartis |
IgE |
Allergic asthma and nasal-polyp competition |
Nucala’s direct biologic competition is strongest from Fasenra. Dupixent and Tezspire exert greater strategic pressure because their labels and clinical positioning can reach patients who do not fit a narrow eosinophil-driven treatment profile.
Fasenra’s eight-week maintenance schedule after loading can be commercially attractive relative to Nucala’s four-week administration. Dupixent’s broad inflammatory-disease portfolio can support payer negotiations and physician cross-specialty adoption.
What are Nucala’s sales and financial trajectory?
Nucala has been one of GSK’s principal growth assets in specialty respiratory medicine.
| Year |
Approximate global sales |
Direction |
| 2021 |
£1.1 billion |
Strong growth after expansion into rare disease and nasal polyps |
| 2022 |
£1.4 billion |
Continued volume and geographic expansion |
| 2023 |
£1.7 billion |
Approximately mid-teens growth |
| 2024 onward |
Growth expected to moderate |
Increasing competitive and exclusivity pressure |
GSK reports Nucala sales within specialty medicines and respiratory disclosures. The product’s revenue trajectory has benefited from:
- Increased biologic use in severe asthma.
- Diagnosis of eosinophilic phenotypes.
- Expansion into CRSwNP.
- Rare-disease pricing and treatment persistence.
- Greater use outside the United States.
- Clinical evidence supporting steroid-sparing treatment.
The largest financial risk is not an immediate patent cliff in 2025. The more relevant risk window is 2027-2030, when U.S. biosimilar entry, European tender pressure and indication-level patent disputes could combine.
What revenue exposure does GSK face at biosimilar entry?
Nucala revenue exposure is material but manageable within GSK’s diversified portfolio. A U.S. biosimilar could affect:
- Net price through payer contracting.
- New-patient share.
- Existing-patient retention.
- Hospital and specialty-pharmacy purchasing.
- International reference pricing.
- The value of later-line and maintenance indications.
A rapid erosion scenario would require FDA-approved biosimilars with broad labels, favorable payer placement and evidence supporting substitution or switching. A slower scenario would result if biosimilar sponsors launch with narrow indications, face patent litigation or encounter physician reluctance to switch stable patients.
Nucala’s multi-indication profile reduces dependence on severe asthma alone. It does not eliminate erosion risk because biosimilar manufacturers may seek the major asthma indication first and later expand through supplemental applications.
What patent litigation and Paragraph IV risks affect Nucala?
Paragraph IV litigation is an ANDA concept and does not directly govern biologics. Nucala biosimilar disputes would proceed under the BPCIA, potentially involving:
- Disclosure of the biosimilar application.
- Exchange of patent information.
- Negotiated selection of patents for immediate litigation.
- Declaratory-judgment actions.
- Preliminary injunction requests.
- Launch-at-risk decisions.
- Separate disputes over later-filed continuation patents.
The most important litigation questions will be whether GSK can assert valid claims covering the proposed biosimilar’s formulation, dosing or manufacturing process and whether the biosimilar sponsor can omit patented indications.
Manufacturing patents may be difficult to enforce against a rival process that uses different cell culture conditions, purification steps or analytical controls. Method-of-use patents may be more vulnerable if the biosimilar label excludes the claimed indication or if physicians prescribe the product for non-patented uses.
What generic or biosimilar launch scenarios exist for Nucala?
Early controlled launch
A biosimilar sponsor launches after November 2027 with a limited label, avoids selected method-of-use patents and targets specialty pharmacies. Erosion is initially concentrated in new starts.
Broad U.S. biosimilar competition
Multiple sponsors enter after regulatory exclusivity and patent settlements. Payers place biosimilars on preferred tiers, reducing Nucala’s price and share across asthma and other indications.
Delayed launch
GSK obtains injunctions or reaches settlements that defer commercial launch beyond regulatory exclusivity. The result depends on patent validity and the scope of the settlement.
European price erosion
European biosimilar entry and hospital tenders reduce net price before U.S. substitution becomes material. The effect is more likely to appear in volume-weighted revenue than in U.S. prescription data.
How does Nucala compare with Fasenra and Dupixent?
Nucala has a mature eosinophil-centered franchise and four approved disease areas. Fasenra has a differentiated dosing schedule and strong AstraZeneca respiratory infrastructure. Dupixent has the broadest type-2 inflammation reach and a larger cross-indication commercial platform.
| Factor |
Nucala |
Fasenra |
Dupixent |
| Core target |
IL-5 |
IL-5 receptor |
IL-4 receptor alpha |
| Severe asthma |
Strong |
Strong |
Strong |
| CRSwNP |
Yes |
Yes |
Yes |
| EGPA |
Yes |
No equivalent broad label |
No |
| HES |
Yes |
No equivalent broad label |
No |
| Dosing convenience |
Monthly or selected administration options |
Every eight weeks for eligible patients |
Varies by indication |
| Main strategic advantage |
Eosinophil-specific and rare-disease breadth |
Dosing and eosinophil depletion |
Broad type-2 disease platform |
| Main risk |
Biosimilar timing and crowded class |
Dupixent and Tezspire competition |
Payer and indication expansion pressure |
Nucala is best positioned where eosinophil biology is central and the physician values disease-specific evidence. It is less advantaged in biomarker-agnostic severe asthma markets.
Key Takeaways
- Nucala is GSK’s mepolizumab-based anti-IL-5 biologic for severe eosinophilic asthma and several eosinophil-driven diseases.
- Global sales rose from about £1.1 billion in 2021 to roughly £1.7 billion in 2023.
- U.S. biologic exclusivity is expected to end on November 4, 2027, with a possible pediatric extension.
- The principal patent risk is likely to come from secondary formulation, dosing, manufacturing and method-of-use claims rather than a single late-expiring composition patent.
- No conventional Paragraph IV ANDA challenge applies. Future disputes will use the BPCIA biosimilar framework.
- Fasenra is Nucala’s closest direct competitor. Dupixent and Tezspire create broader strategic pressure.
- CRSwNP, EGPA and HES diversify revenue but do not fully protect Nucala from biosimilar erosion in severe asthma.
- The primary commercial risk window is 2027-2030.
FAQs About Nucala Patent and Market Risk
Is Nucala a biologic or a generic drug?
Nucala is a biologic monoclonal antibody. A follow-on product would be a biosimilar, not a conventional generic approved through an ANDA.
Can a Nucala biosimilar launch before 2027?
FDA approval is generally barred during the 12-year reference-product exclusivity period. Patent litigation or settlement terms could delay launch beyond the regulatory date.
Does Nucala have orphan-drug protection?
Nucala received orphan-related protection for rare indications such as hypereosinophilic syndrome and EGPA. That protection is indication-specific and does not create a blanket market monopoly across all Nucala uses.
Which Nucala indication has the greatest commercial value?
Severe eosinophilic asthma remains the principal revenue base. CRSwNP is the most important expansion market by patient opportunity, while EGPA and HES contribute smaller but higher-specialization revenue streams.
Is Nucala interchangeable with Fasenra or Dupixent?
No. They are different biologics with different targets, dosing schedules, labels and clinical evidence. Substitution requires a prescribing decision and payer or formulary support.
References
- U.S. Food and Drug Administration. (2024). Purple Book: Database of licensed biological products. https://purplebooksearch.fda.gov/
- U.S. Food and Drug Administration. (2024). Nucala prescribing information. GSK.
- U.S. Food and Drug Administration. (2024). Regulatory considerations in demonstrating biosimilarity to a reference product.
- GSK plc. (2024). Annual report 2023.
- GSK plc. (2023). Annual report 2022.
- U.S. Food and Drug Administration. (2021). FDA approves Nucala for eosinophilic granulomatosis with polyangiitis.
- U.S. Food and Drug Administration. (2020). FDA approves Nucala for hypereosinophilic syndrome.
