List of Excipients in Branded Drug USTEKINUMAB-AEKN

Ustekinumab-AEKN Excipient Strategy and Commercial Opportunities

Last updated: August 9, 2026

Ustekinumab-aekn, marketed by Amgen as Wezlana, is an FDA-approved biosimilar and interchangeable biosimilar to Stelara (ustekinumab). Its excipient strategy is conservative: the product uses a conventional histidine buffer system, sucrose as a stabilizer, polysorbate 80 as a surfactant, methionine as an oxidation-control excipient, and water for injection. The commercial opportunity is driven less by novel excipient differentiation than by lower-cost supply, interchangeability, device execution, formulation reliability, and access to Stelara’s large immunology market.

What is ustekinumab-aekn and how is it regulated?

Ustekinumab-aekn is a recombinant human monoclonal antibody targeting the p40 subunit shared by interleukin-12 and interleukin-23. It is approved for the same principal indications as Stelara, including:

• Moderate-to-severe plaque psoriasis
• Psoriatic arthritis
• Moderately to severely active Crohn’s disease
• Moderately to severely active ulcerative colitis

FDA approved Wezlana under the biosimilar pathway in October 2024. The product received an interchangeable designation, allowing pharmacy-level substitution where state law permits and subject to payer and institutional protocols.[1]

What dosage forms and strengths are available?

Wezlana is supplied in intravenous and subcutaneous presentations:

Presentation	Strength	Primary use
Single-dose vial	130 mg/26 mL	Intravenous induction for Crohn’s disease and ulcerative colitis
Pre-filled syringe	45 mg/0.5 mL	Subcutaneous maintenance
Pre-filled syringe	90 mg/1.0 mL	Subcutaneous maintenance
Single-dose pre-filled pen	45 mg/0.5 mL	Subcutaneous maintenance
Single-dose pre-filled pen	90 mg/1.0 mL	Subcutaneous maintenance

The IV presentation is administered by a health-care professional. The subcutaneous products support self-administration after appropriate training.

What excipients are used in ustekinumab-aekn?

The commercial formulation uses excipients commonly accepted for monoclonal antibody products. The formulation is designed to control pH, reduce aggregation, limit oxidation, and maintain protein stability during refrigerated storage and administration.

Excipient or formulation component	Functional role
L-histidine	Primary buffering agent
L-histidine hydrochloride monohydrate	Buffer capacity and pH control
Sucrose	Protein stabilizer and tonicity contributor
Polysorbate 80	Surfactant that limits adsorption and interfacial aggregation
L-methionine	Oxidation-control excipient
Water for injection	Diluent and vehicle

The product is preservative-free and supplied as a single-dose biologic. The excipient profile is materially aligned with the reference product’s established formulation architecture, which reduces clinical and regulatory risk associated with formulation changes.[2]

Why is histidine used in the formulation?

Histidine is widely used in antibody formulations because it provides buffering near the mildly acidic pH range commonly selected for immunoglobulin stability. Histidine buffer systems can help control pH shifts during refrigerated storage and reduce the risk of chemical degradation.

For a biosimilar, the commercial value of histidine is primarily functional rather than proprietary. Histidine is a well-established pharmaceutical excipient with a broad supply base. Its use supports comparability and manufacturing transfer without creating a significant novel-excipient regulatory burden.

What is the role of sucrose?

Sucrose acts as a stabilizer by helping maintain the native structure of the antibody during freezing, shipping, agitation, and temperature excursions. It also contributes to solution tonicity.

Sucrose is commercially attractive because it is inexpensive, globally available, and well characterized in parenteral biologics. Its use does not create meaningful formulation differentiation, but it supports cost control and manufacturing scale-up.

Why is polysorbate 80 important?

Polysorbate 80 reduces protein adsorption to container surfaces and limits aggregation at air-liquid and liquid-solid interfaces. It is particularly important for high-value monoclonal antibodies delivered in low-volume pre-filled syringes and pens.

Polysorbate 80 also creates supply-chain and quality-control requirements. The excipient can undergo hydrolysis and oxidation, generating degradation products that may affect protein stability or particle formation. Commercial manufacturers therefore need tight controls over:

• Peroxide levels
• Fatty-acid composition
• Hydrolysis products
• Lot-to-lot variability
• Storage conditions
• Compatibility with the syringe, needle, and autoinjector materials

Polysorbate 80 is a likely focus for supplier qualification, incoming testing, and stability monitoring, even though it is not a differentiating ingredient.

What is the role of methionine?

Methionine can function as an oxidation sacrificial agent. It may reduce oxidation of susceptible amino-acid residues in the antibody, particularly methionine residues located in or near regions that affect product quality.

Its inclusion supports product stability during storage and handling. The commercial opportunity is strongest in excipient-grade methionine supply, impurity control, and formulation analytics rather than in a standalone proprietary product.

How does the ustekinumab-aekn formulation compare with Stelara?

The central biosimilar formulation strategy is similarity, not excipient innovation. Wezlana’s inactive-ingredient profile is substantially aligned with the reference product, which supports the FDA’s determination that the products are highly similar and have no clinically meaningful differences in safety, purity, or potency.[1,2]

Attribute	Wezlana	Stelara	Commercial implication
Active ingredient	Ustekinumab-aekn	Ustekinumab	Biosimilar substitution opportunity
Buffer system	Histidine-based	Histidine-based	Low formulation novelty
Stabilizer	Sucrose	Sucrose	Established supply chain
Surfactant	Polysorbate 80	Polysorbate 80	Quality and oxidation monitoring required
Oxidation control	Methionine-containing formulation	Methionine-containing formulation	Supports stability alignment
Preservative	None	None	Single-dose packaging
Administration	IV and subcutaneous	IV and subcutaneous	Broad indication and channel coverage
Interchangeability	FDA designated	Reference product	Supports substitution potential

The absence of a novel excipient limits opportunities to claim composition-based differentiation. It also reduces regulatory risk and simplifies manufacturing comparability.

What excipient patents protect ustekinumab-aekn?

The principal intellectual-property value around ustekinumab-aekn is not expected to reside in a novel excipient. The product is a biosimilar to a reference antibody with an established formulation. Relevant protection may instead involve:

• Reference-product formulation patents
• Antibody composition and sequence patents
• Manufacturing and cell-culture processes
• Purification methods
• Delivery devices
• Container-closure systems
• Labeling and method-of-use claims
• Supplier-specific excipient or component specifications

FDA biologics are not listed in the Orange Book in the same way as small-molecule drugs. Biologic exclusivity and patent information are addressed through the Purple Book and related patent-dispute mechanisms under the Biologics Price Competition and Innovation Act.[3]

Does an excipient patent create a major entry barrier?

Usually, no. A formulation patent can create a meaningful litigation or design-around risk if it covers a specific combination of protein concentration, pH, surfactant level, stabilizer, or storage condition. Its strength depends on claim scope, written-description support, validity, and whether the biosimilar product practices the claims.

For ustekinumab-aekn, the most commercially relevant risk is likely to involve Stelara-related formulation and device patents rather than the use of histidine, sucrose, polysorbate 80, or methionine as isolated excipients. These ingredients are widely used and generally difficult to monopolize broadly.

When does ustekinumab lose exclusivity?

The reference product’s U.S. regulatory exclusivity expired before Wezlana approval. The main commercial timing issue is patent-controlled entry rather than biologic regulatory exclusivity.

Milestone	Timing
Stelara U.S. approval	September 2009
Twelve-year reference-product exclusivity	Expired in 2021
U.S. composition patent protection	Principal protection expired before biosimilar launch
Wezlana FDA approval	October 2024
Expected Amgen U.S. commercial launch	January 2025 under the announced settlement framework
Interchangeable designation	Granted at approval

Janssen and Amgen reached a settlement covering ustekinumab-aekn entry in the United States. The settlement allowed Amgen to launch in the United States on or after January 1, 2025, subject to the agreement’s terms.[4]

Patent expiry analysis must be performed at the claim and jurisdiction level. A nominal expiration date does not necessarily determine the earliest commercial launch date because patent settlements, pediatric extensions, terminal disclaimers, regulatory exclusivity, and product-specific litigation can change the effective entry date.

What commercial opportunities exist for excipients used in ustekinumab-aekn?

The excipient opportunity is primarily a supply, quality, and delivery opportunity.

1. Polysorbate 80 supply and quality control

Polysorbate 80 is the most commercially sensitive excipient in the formulation. Suppliers can compete through:

• Low-peroxide grades
• Improved lot consistency
• Tighter fatty-acid specifications
• Better oxidation profiles
• Reduced particulate risk
• Global dual sourcing
• Stronger documentation for biologics manufacturing

A supplier able to demonstrate stable performance in pre-filled syringes and autoinjectors may obtain a strategic advantage even without owning a patent.

2. High-purity histidine systems

Histidine and histidine hydrochloride are commodity-like ingredients, but biologics manufacturers require pharmaceutical-grade material with reliable impurity profiles and consistent pH performance. Opportunities exist in:

• Ready-to-use buffer concentrates
• Single-use manufacturing formats
• Low-endotoxin excipient grades
• Validated global supply
• Formulation development services
• Stability packages for biosimilar manufacturers

3. Methionine as an oxidation-control component

Methionine can support formulation robustness, particularly when manufacturing or shipping conditions increase oxidative stress. Suppliers may differentiate through:

• Low-impurity material
• Consistent optical purity
• Low bioburden and endotoxin
• Stability data in antibody formulations
• Compatibility with high-concentration products

4. Container-closure and device compatibility

The commercial opportunity extends beyond the liquid formulation. Wezlana’s pre-filled syringes and pens require compatibility among:

• Polysorbate 80
• Silicone oil
• Needle adhesives
• Elastomer components
• Glass or polymer barrels
• Autoinjector contact materials

Container-closure interaction can influence subvisible particles, protein adsorption, extractables, leachables, and delivered dose. Component suppliers that reduce these risks can support lifecycle-management and manufacturing-transfer programs.

5. Cold-chain and excursion management

Ustekinumab products are refrigerated biologics. Excipient and packaging strategies that improve stability during short temperature excursions can reduce waste and improve distribution economics. Commercial products may include:

• Validated temperature-monitoring systems
• Cold-chain packaging
• Stability-indicating analytical methods
• Shipping qualification services
• Excursion-management protocols

How large is the commercial market for ustekinumab biosimilars?

Stelara generated approximately $10 billion or more in annual global sales in the years immediately preceding U.S. biosimilar entry, making it one of the largest near-term immunology biosimilar markets.[5] The principal revenue pools are:

• Dermatology
• Rheumatology
• Gastroenterology
• Hospital-based induction treatment
• Specialty pharmacy maintenance therapy

The subcutaneous maintenance market is especially important because it supports recurring prescription volume and self-administration. The IV induction segment is smaller in unit volume but has high institutional relevance and can strengthen contracting with integrated delivery networks.

Which companies are challenging Stelara?

Amgen is the most commercially advanced U.S. entrant with ustekinumab-aekn. Other companies have pursued ustekinumab biosimilar programs or regulatory filings in international markets, including companies connected with major biosimilar developers such as Samsung Bioepis, Celltrion, and Fresenius Kabi. Market participation varies by jurisdiction, approval status, and settlement terms.

Competition is likely to center on:

• Net price discounts
• Payer formulary placement
• Interchangeability
• Patient-support services
• Specialty-pharmacy access
• Device usability
• Supply reliability
• Gastroenterology contracting

What generic entry risks exist for ustekinumab-aekn?

Ustekinumab-aekn faces biosimilar competition risk rather than conventional generic substitution risk. The main risks are commercial and operational.

Risk	Effect on commercial opportunity
Multiple biosimilar entrants	Reduces achievable net price
Payer consolidation	Increases rebate pressure
Limited automatic substitution	Slows pharmacy-level switching
Physician familiarity with Stelara	Raises conversion costs
Device preference	Can influence persistence
Manufacturing deviations	Creates supply interruptions
Polysorbate degradation	May increase aggregation or particles
Patent litigation	Can delay or constrain launch
Indication-specific contracting	May fragment market access

Interchangeability improves substitution potential but does not guarantee rapid conversion. State substitution rules, payer policies, prescriber behavior, patient-support programs, and contracting terms remain decisive.

How strong is the ustekinumab-aekn patent and formulation position?

Ustekinumab-aekn has a strong regulatory position but a limited opportunity for formulation-based exclusivity. Its advantages are:

• FDA biosimilar approval
• Interchangeable designation
• Multiple strengths and delivery formats
• Coverage of major Stelara indications
• Early U.S. entry under settlement
• Established excipient architecture
• Broad manufacturing and distribution potential

Its limitations are:

• No meaningful composition-of-matter exclusivity for the biosimilar
• Exposure to reference-product formulation patents
• Exposure to device and container-closure claims
• Expected price competition
• Dependence on biologics manufacturing capacity
• Limited ability to distinguish through common excipients

The strongest commercial moat is therefore execution. A supplier or manufacturer that can provide consistent polysorbate 80 quality, robust cold-chain performance, reliable fill-finish, and user-friendly delivery devices may capture value even where the core formulation is not patent differentiated.

What licensing and partnership opportunities exist?

Potential licensing opportunities are concentrated in manufacturing and commercial infrastructure rather than excipient ownership.

Excipient and formulation partnerships

Companies may license or supply:

• High-purity polysorbate 80
• Stabilized surfactant systems
• Histidine buffer platforms
• Oxidation-control excipient packages
• Analytical methods for aggregation and particles
• Formulation-screening platforms

Device partnerships

Strategic opportunities include:

• Pre-filled syringe systems
• Autoinjectors
• Human-factors engineering
• Needle-safety systems
• Connected injection devices
• Container-closure technologies

Commercial partnerships

Ustekinumab biosimilars can support agreements with:

• Specialty pharmacies
• Gastroenterology networks
• Dermatology purchasing groups
• Integrated delivery networks
• Payers and pharmacy benefit managers
• International distributors

The most valuable agreements are likely to combine supply assurance with payer access. An excipient supplier that secures a position in the approved commercial formulation can benefit from recurring demand, but switching costs may be high once the product is qualified and validated.

What FDA regulatory issues affect excipient strategy?

FDA expects biosimilar manufacturers to demonstrate that differences in inactive ingredients do not affect safety, purity, or potency. Excipient changes can trigger additional analytical, stability, immunogenicity, or clinical assessment requirements depending on their potential effect on product quality.[2]

Key regulatory controls include:

• Excipient identity and grade
• Supplier qualification
• Certificate-of-analysis review
• Endotoxin and bioburden controls
• Peroxide and degradation-product testing
• Compatibility with primary packaging
• Stability under labeled storage conditions
• Control of visible and subvisible particles
• Comparability after manufacturing changes

A novel excipient would increase development and regulatory complexity. For ustekinumab-aekn, a conventional excipient strategy is commercially rational because it minimizes the risk of a clinically meaningful difference and supports a faster biosimilar pathway.

What are the best commercial strategies for ustekinumab-aekn?

The highest-value strategy is a cost-efficient, quality-controlled biosimilar platform with strong delivery execution.

Priority actions include:

1. Maintain dual-source qualification for polysorbate 80 and other critical excipients.
2. Use supplier specifications that address oxidation, hydrolysis, particles, and lot consistency.
3. Protect device compatibility through early container-closure studies.
4. Build interchangeable-product contracting around automatic substitution where permitted.
5. Target gastroenterology and dermatology channels with separate access strategies.
6. Use patient-support programs to reduce switching friction.
7. Preserve flexibility for future high-concentration or next-generation delivery systems.
8. Monitor Stelara formulation, device, and manufacturing patents by jurisdiction.
9. Treat fill-finish capacity as a commercial constraint, not only a manufacturing issue.
10. Avoid unnecessary excipient changes that could increase comparability and regulatory costs.

Key Takeaways

• Ustekinumab-aekn is Amgen’s FDA-approved interchangeable biosimilar to Stelara.
• Its excipients are conventional: histidine, histidine hydrochloride, sucrose, polysorbate 80, methionine, and water for injection.
• The formulation strategy prioritizes similarity, stability, and regulatory predictability rather than novel excipient protection.
• Polysorbate 80 is the most important excipient from a quality and supply-chain perspective.
• The principal U.S. commercial opportunity began with the January 2025 launch window established under the Amgen-Janssen settlement.
• Patent risk is more likely to involve reference-product formulation, device, and manufacturing claims than broad ownership of common excipients.
• The global Stelara market exceeded $10 billion annually before biosimilar erosion, creating a large but highly competitive opportunity.
• Commercial success will depend on price, payer access, interchangeability, device performance, supply reliability, and manufacturing quality.

FAQs

Can ustekinumab-aekn use a different surfactant from polysorbate 80?

A different surfactant could be developed, but it would require extensive comparability and stability support. Polysorbate 80 is commercially preferred because it is established in monoclonal antibody formulations and aligns with the reference-product formulation strategy.

Is ustekinumab-aekn listed in the Orange Book?

No. As a biologic, ustekinumab-aekn is addressed through the FDA biologics framework and the Purple Book rather than standard Orange Book listing procedures.

Which excipient creates the greatest manufacturing risk?

Polysorbate 80 generally creates the greatest risk because oxidation, hydrolysis, lot variability, and interaction with packaging components can affect aggregation and particulate levels.

Can an excipient supplier obtain patent protection around a ustekinumab formulation?

Potentially, but broad claims covering common excipients such as sucrose, histidine, or polysorbate 80 would be difficult to sustain. Stronger claims would likely require a specific concentration range, stability result, packaging interaction, manufacturing process, or delivery configuration.

Will interchangeable status guarantee rapid biosimilar substitution?

No. Interchangeability supports substitution under applicable law, but payer formularies, state pharmacy rules, prescriber practices, contracting, patient preference, and product availability determine the rate of market conversion.

References

1. U.S. Food and Drug Administration. (2024). Wezlana (ustekinumab-aekn) prescribing information.
2. U.S. Food and Drug Administration. (2019). Development of therapeutic protein biosimilars: Comparative analytical assessment and other quality-related considerations: Guidance for industry.
3. U.S. Food and Drug Administration. (2024). Purple Book: Database of licensed biological products.
4. Amgen Inc. (2023). Amgen announces settlement with Janssen regarding biosimilar ustekinumab.
5. Johnson & Johnson. (2024). Annual report and financial results.