List of Excipients in Branded Drug FASENRA

FASENRA Excipient Strategy and Commercial Opportunities

Last updated: September 15, 2026

FASENRA (benralizumab) is a subcutaneous anti-interleukin-5 receptor alpha monoclonal antibody marketed by AstraZeneca for severe eosinophilic asthma. Its formulation uses a conventional biologic excipient system: histidine buffering, trehalose stabilization, polysorbate 20 as surfactant, and water for injection. The main commercial opportunities are in biosimilar development, antibody-drug product manufacturing, excipient supply, device integration, and lifecycle management rather than in simple substitution of individual formulation ingredients.

FASENRA generated approximately $1.5 billion in AstraZeneca sales in 2023, making it a commercially significant biologic with a sizeable future biosimilar and manufacturing market.[1]

What excipients are used in FASENRA?

The FASENRA formulation contains four principal excipient categories:

Component	Function in formulation	Commercial relevance
Benralizumab	Anti-IL-5 receptor alpha monoclonal antibody	Active biologic
Histidine and histidine hydrochloride monohydrate	Buffer system	Controls formulation pH and protein stability
Trehalose dihydrate	Stabilizer and tonicity contributor	Reduces aggregation and supports liquid stability
Polysorbate 20	Nonionic surfactant	Reduces interfacial stress, adsorption, and agitation-induced aggregation
Water for injection	Vehicle	Injectable medium

The U.S. prescribing information identifies the product as a sterile, preservative-free solution containing 30 mg of benralizumab per mL. The formulation has a target pH of approximately 5.5.[2]

FASENRA is supplied in a single-dose prefilled syringe and in an autoinjector presentation in certain markets. The product is administered subcutaneously, generally every eight weeks after an initial loading schedule.[2]

Why is the FASENRA excipient system commercially important?

The formulation uses widely available excipients, but biologic manufacturers cannot treat them as interchangeable commodities. Small differences in grade, purity, peroxide content, trace metals, particle burden, or extractables can affect antibody quality.

Histidine buffer

Histidine is commonly used in monoclonal antibody products because it provides buffering in a mildly acidic pH range and generally has favorable compatibility with proteins. For a benralizumab biosimilar, the buffer system is a likely starting point because formulation similarity can reduce analytical and clinical comparability risk.

Commercial opportunities include:

• Pharmaceutical-grade histidine supply
• Histidine hydrochloride monohydrate supply
• Low-endotoxin and low-bioburden grades
• Global dual sourcing
• Excipient qualification packages
• Stability and compatibility studies for biosimilar developers

The relevant business value is not the chemical itself. It is the ability to provide consistent material attributes across manufacturing sites and regulatory regions.

Trehalose dihydrate

Trehalose supports the physical stability of monoclonal antibodies by reducing structural stress during storage and handling. It can contribute to isotonicity and help limit aggregation during temperature excursions.

A biosimilar developer may initially replicate the trehalose concentration used in the reference product. A different concentration or stabilizer can create additional comparability work, especially where the change affects:

• Aggregation
• Subvisible particles
• Charge variants
• Viscosity
• Freeze-thaw behavior
• Syringeability
• Container closure compatibility

Trehalose suppliers with strong control of water content, endotoxin, microbial limits, and lot-to-lot consistency are positioned to support antibody manufacturers.

Polysorbate 20

Polysorbate 20 is the most technically sensitive component in the FASENRA excipient system. It protects the antibody against adsorption and interfacial degradation during filling, transport, and administration.

Potential failure modes include:

• Oxidative degradation
• Hydrolysis
• Formation of fatty-acid particles
• Interaction with trace metals
• Loss of surfactant concentration
• Protein aggregation
• Visible or subvisible particulate formation

For manufacturers, polysorbate 20 is not a simple formulation input. Supplier selection, peroxide control, storage conditions, analytical testing, and container interaction are central to product quality.

Commercial suppliers can differentiate through:

• Low-peroxide polysorbate 20
• Defined fatty-acid distribution
• Improved oxidation control
• Pharmaceutical-grade documentation
• Container compatibility data
• Stability-indicating analytical methods
• Regional supply resilience

Alternative surfactants, including polysorbate 80 or newer protein-stabilizing surfactants, may be evaluated during biosimilar development. A change from polysorbate 20 would require a strong technical rationale and extensive comparability evidence.

What formulation characteristics must a FASENRA biosimilar match?

A biosimilar does not need to use every identical excipient, but the total product must demonstrate no clinically meaningful differences from the reference product. For FASENRA, the most commercially relevant comparability targets are:

Attribute	Why it matters
Protein concentration	Influences dose accuracy and injection volume
pH	Affects charge profile, aggregation, and chemical degradation
Osmolality	Affects injection tolerability
Histidine concentration	Influences buffering capacity
Trehalose concentration	Influences stability and tonicity
Polysorbate 20 level	Influences aggregation and particle formation
Subvisible particles	Important for injectable biologics
Aggregates	Can affect potency and immunogenicity risk
Charge variants	May affect functional comparability
Glycosylation	Relevant to structure and mechanism
Potency	Must align with IL-5 receptor alpha binding and cell-based activity
Container closure	Affects sterility, adsorption, and extractables

The highest-value development strategy is usually to begin with a reference-like formulation. A differentiated excipient system may reduce long-term manufacturing cost or improve stability, but it increases analytical, process, and regulatory risk.

What commercial opportunities exist in FASENRA excipients?

Excipient supply

The direct excipient market is modest relative to the value of the finished biologic. The commercial opportunity lies in recurring, qualified supply. Once a supplier is incorporated into a validated manufacturing process, replacement can trigger comparability studies, stability work, and regulatory change controls.

Suppliers with the strongest positioning will offer:

• Multiple manufacturing sites
• Global regulatory documentation
• Low particulate and endotoxin profiles
• Long-term supply agreements
• Technical support for biologic formulation
• Support for extractables and leachables testing
• Data packages for U.S., European, Japanese, and Chinese submissions

Contract development and manufacturing

FASENRA-style products require expertise in:

• Mammalian-cell antibody production
• Low-shear formulation
• Aseptic filling
• Prefilled syringe assembly
• Autoinjector integration
• Cold-chain distribution
• High-sensitivity particle testing

Contract development and manufacturing organizations can capture value by offering an integrated package rather than separate formulation or filling services.

Device and combination-product opportunities

FASENRA’s subcutaneous route creates commercial opportunities in:

• Prefilled syringes
• Autoinjectors
• Needle-safety systems
• Low-volume delivery systems
• Home-injection training
• Digital adherence tools
• Cold-chain packaging

The device can be a competitive barrier even when the underlying antibody is no longer patent-protected. A biosimilar that requires a different injection workflow may face market-access disadvantages against a familiar at-home presentation.

When does FASENRA lose exclusivity?

FASENRA received U.S. FDA approval in November 2017. As a licensed biologic, it benefits from 12 years of reference-product exclusivity under the Biologics Price Competition and Innovation Act. The principal U.S. reference-product exclusivity period therefore runs to approximately November 2029, subject to the statutory framework and FDA determinations.[3]

Biologic exclusivity is different from small-molecule exclusivity:

Issue	FASENRA
Regulatory pathway	Biologics License Application
Biosimilar pathway	Section 351(k)
Orange Book listing	No
Relevant FDA database	Purple Book
Reference product	Benralizumab
U.S. approval	November 2017
Reference exclusivity horizon	Approximately November 2029
Generic substitution	Not automatic in the same manner as an AB-rated tablet
Interchangeability	Requires a separate FDA determination

Patent expiration may occur later than regulatory exclusivity and can depend on patent scope, patent-term adjustment, patent-term extension, terminal disclaimers, and litigation outcomes. The relevant patent estate includes antibody, binding, therapeutic-use, formulation, and manufacturing claims. Formulation claims covering histidine, trehalose, polysorbate 20, or their specific concentrations would need to be assessed separately from the regulatory exclusivity period.

What patents protect FASENRA and its formulation?

FASENRA’s principal intellectual-property value is expected to reside in antibody and use claims rather than in the basic excipients individually. Histidine, trehalose, polysorbate 20, and water for injection are established pharmaceutical materials and generally have limited standalone exclusivity value.

Potential claim categories include:

1. Anti-IL-5 receptor alpha antibodies.
2. Specific antibody sequences and variants.
3. Binding to IL-5 receptor alpha.
4. Treatment of eosinophilic diseases.
5. Dosing schedules, including extended-interval administration.
6. Subcutaneous delivery.
7. Formulations with defined pH, stabilizer, and surfactant concentrations.
8. Container closure and delivery-device combinations.
9. Manufacturing and purification processes.

A patent challenge focused solely on excipients may have limited commercial impact if the biosimilar sponsor can use a non-infringing but analytically comparable formulation. The stronger barriers are likely to involve antibody sequence, method-of-use, dosing, and device-related claims.

What is the Paragraph IV equivalent for FASENRA?

FASENRA does not use the Hatch-Waxman Paragraph IV process applicable to small-molecule drugs. A biosimilar sponsor files under Section 351(k) and may participate in the BPCIA patent-exchange process, commonly called the patent dance.

A biosimilar sponsor can face disputes involving:

• Reference-product patents listed in the Purple Book or otherwise asserted by the sponsor
• Notice of commercial marketing
• Patent-infringement litigation under 35 U.S.C. § 271(e)(2)
• Manufacturing-process patents
• Formulation patents
• Method-of-use patents
• Interchangeability and labeling strategy

The absence of an Orange Book listing does not eliminate patent risk. It changes the procedural framework and reduces the predictability associated with an approved small-molecule product’s listed patents.

How strong is the FASENRA formulation patent estate?

The formulation estate is potentially meaningful but is unlikely to be the sole barrier to biosimilar entry. A conventional formulation containing histidine, trehalose, polysorbate 20, and water for injection may be difficult to protect broadly because each component is widely used in antibody products.

Strength depends on claim specificity:

Claim type	Relative defensive value
Broad use of histidine in an antibody formulation	Low
Broad use of trehalose as a stabilizer	Low
Broad use of polysorbate 20	Low to moderate
Defined concentrations and pH range	Moderate
Specific stability profile or degradation limit	Moderate
Combination with a particular antibody sequence	Moderate to high
Formulation plus autoinjector or delivery system	Moderate to high
Manufacturing process producing a defined quality profile	Moderate to high

The most defensible formulation claims are usually narrow claims tied to a specific antibody, concentration range, stability result, or manufacturing process.

What generic and biosimilar launch scenarios exist?

Three launch scenarios are commercially relevant.

Scenario 1: Reference-like biosimilar formulation

A sponsor uses the same broad excipient architecture and develops a prefilled syringe. This approach minimizes formulation risk and supports a conventional biosimilar strategy. Price competition would likely be the primary differentiator.

Scenario 2: Device-led biosimilar

A sponsor uses a different autoinjector or more convenient home-administration system. The product may gain payer or patient preference, but device development and human-factors validation add cost.

Scenario 3: Formulation-differentiated product

A sponsor develops a higher-concentration or more stable formulation with reduced injection volume or improved temperature tolerance. This could support lifecycle differentiation, but it would require extensive comparability evidence and may encounter formulation or device patents.

A conventional tablet-style generic launch is not applicable. The relevant competition is among biosimilars, authorized or licensed biologic alternatives, and potentially new anti-eosinophilic biologics.

How does FASENRA compare with competing asthma biologics?

Product	Target	Typical dosing pattern	Primary competitive issue
FASENRA	IL-5 receptor alpha	Every eight weeks after loading	Dosing convenience and eosinophil depletion
NUCALA	IL-5	Generally every four weeks	Established biologic franchise
DUPIXENT	IL-4 receptor alpha	Every two or four weeks, depending on indication	Broader type 2 inflammatory indications
TEZSPIRE	TSLP	Every four weeks	Broad severe-asthma positioning
CINQAIR	IL-5	Intravenous every four weeks	Infusion-based administration

FASENRA’s eight-week maintenance schedule is a formulation and commercial advantage. It reduces administration frequency, but the product remains dependent on reliable subcutaneous delivery, cold-chain performance, and patient acceptance of injection devices.

What FDA and regulatory status affects commercial opportunities?

FASENRA is an FDA-approved biologic for add-on maintenance treatment of severe asthma with an eosinophilic phenotype. Its regulatory profile supports recurring demand from specialty care and home administration.[2]

Commercial opportunities are shaped by:

• FDA biosimilar approval under Section 351(k)
• Interchangeability designation
• Payer formulary placement
• Specialty-pharmacy distribution
• Injection-device usability
• Pediatric labeling
• International reference-product requirements
• Cold-chain logistics
• Manufacturing capacity

A biosimilar with interchangeability may receive stronger substitution potential, but payer policy and contracting may remain more important than regulatory status alone.

What manufacturing and IP barriers affect FASENRA competition?

The largest barriers are likely to be:

• High-quality antibody production
• Consistent glycosylation and charge profiles
• Low aggregate and particle levels
• Polysorbate degradation control
• Aseptic filling
• Prefilled-device assembly
• Long-term refrigerated stability
• Global regulatory comparability
• Patent litigation
• Commercial payer access

Excipient cost is unlikely to determine the final market outcome. The more important economic variables are yield, batch failure rates, fill-finish efficiency, device cost, clinical development expense, and discounts required to secure formulary access.

Key Takeaways

• FASENRA uses a conventional biologic formulation based on histidine, trehalose dihydrate, polysorbate 20, and water for injection.
• Polysorbate 20 is the most technically sensitive excipient because oxidation and degradation can affect particles, aggregation, and stability.
• Excipient suppliers can create value through pharmaceutical-grade consistency, low-peroxide surfactants, regulatory documentation, and supply security.
• The main commercial opportunity is the future benralizumab biosimilar market, not standalone excipient substitution.
• FASENRA received U.S. approval in 2017 and has a reference-product exclusivity horizon extending approximately to 2029.
• FASENRA is governed by the biosimilar framework, not the Orange Book Paragraph IV framework.
• Device integration, home administration, manufacturing quality, and method-of-use patents may present stronger barriers than the basic excipient composition.
• A reference-like formulation is the lowest-risk biosimilar strategy; a differentiated formulation may support premium positioning but increases regulatory and IP exposure.
• AstraZeneca’s commercial position is supported by extended-interval dosing, an established severe-asthma franchise, and a large biologic revenue base.

FAQs

Is polysorbate 20 in FASENRA?

Yes. Polysorbate 20 is listed as a surfactant in the FASENRA formulation.

Does FASENRA contain a preservative?

No. FASENRA is supplied as a sterile, preservative-free injectable solution.

Can a benralizumab biosimilar use different excipients?

Yes. A biosimilar can use different excipients if analytical and clinical evidence demonstrates no clinically meaningful differences from the reference product.

Is FASENRA listed in the Orange Book?

No. FASENRA is a biologic, so its regulatory and patent framework is associated with the Purple Book and the BPCIA rather than the Orange Book.

Which FASENRA excipient has the greatest formulation risk?

Polysorbate 20 generally presents the greatest formulation-control risk because oxidation, hydrolysis, and particle formation can affect monoclonal-antibody stability.

References

1. AstraZeneca PLC. (2024). Annual report and Form 20-F 2023. AstraZeneca.

2. U.S. Food and Drug Administration. (2024). FASENRA (benralizumab) injection: Prescribing information. AstraZeneca Pharmaceuticals LP.

3. U.S. Food and Drug Administration. (2024). Purple Book: Lists of licensed biological products with reference product exclusivity and biosimilarity or interchangeability evaluations. FDA.