List of Excipients in Branded Drug SELARSDI

Selarsdi Excipient Strategy and Commercial Opportunities: Ustekinumab-aekn Biosimilar Analysis

Last updated: September 8, 2026

Selarsdi, or ustekinumab-aekn, is a subcutaneous biosimilar to Stelara (ustekinumab) developed by Alvotech and commercialized in the United States by Teva Pharmaceuticals. Its excipient system uses a conventional biologic formulation built around histidine buffering, sucrose stabilization, polysorbate 80 surfactant protection, and water for injection. The commercial opportunity is strongest in interchangeable-biosimilar substitution, payer-driven Stelara erosion, high-volume maintenance dosing, and differentiated delivery or packaging rather than in a novel excipient composition. [1,2]

What is Selarsdi and who commercializes it?

Selarsdi is a monoclonal antibody biosimilar referencing Stelara, the interleukin-12 and interleukin-23 antagonist ustekinumab. The FDA approved Selarsdi in April 2024 for the same principal indications as Stelara:

• Moderate-to-severe plaque psoriasis in adults and pediatric patients six years and older
• Active psoriatic arthritis
• Moderate-to-severe Crohn's disease
• Moderate-to-severe ulcerative colitis

Selarsdi is marketed by Teva Pharmaceuticals and is manufactured under the Alvotech partnership. The FDA designated Selarsdi interchangeable with Stelara, allowing pharmacy-level substitution where state law permits and subject to payer and formulary rules. [1,3]

Attribute	Selarsdi
Active ingredient	Ustekinumab-aekn
Reference product	Stelara, ustekinumab
Biologic class	Human monoclonal antibody
Mechanism	Binds the p40 subunit shared by IL-12 and IL-23
FDA approval	April 2024
FDA status	Biosimilar and interchangeable biosimilar
Administration	Subcutaneous injection; IV induction for Crohn's disease and ulcerative colitis
Commercial sponsors	Alvotech and Teva
Primary opportunity	Lower-cost substitution for Stelara
Principal formulation risk	Aggregation, oxidation, particles, and surfactant degradation

What excipients are used in Selarsdi?

Selarsdi's prefilled syringe formulation contains the following inactive ingredients:

Excipient	Primary formulation function
L-histidine	Buffering and pH control
L-histidine hydrochloride monohydrate	Conjugate buffer component
Sucrose	Tonicity adjustment and protein stabilization
Polysorbate 80	Interfacial stabilization and aggregation control
Water for injection	Vehicle

The formulation has a mildly acidic pH range, reported in the FDA labeling at approximately pH 5.5 to 6.5. Selarsdi is supplied in 45 mg/0.5 mL and 90 mg/1.0 mL prefilled syringe presentations for subcutaneous administration. [1]

The excipient profile closely follows established monoclonal-antibody formulation practice. It does not rely on a high-risk or unusual excipient such as arginine, methionine, trehalose, polyethylene glycol, or a novel surfactant. That design reduces regulatory complexity and supports comparability to Stelara.

Why is the Selarsdi excipient system commercially important?

Excipient selection affects biosimilar development in four commercial areas: analytical similarity, supply reliability, injection experience, and patent exposure.

Analytical similarity

For a biosimilar, the formulation must support a highly similar product without introducing clinically meaningful differences. Histidine and sucrose are widely used in antibody products and are generally compatible with a regulatory strategy focused on structural and functional comparability.

The formulation must control:

• High-molecular-weight aggregates
• Subvisible and visible particles
• Deamidation and oxidation
• Fragmentation
• Adsorption to container surfaces
• Protein concentration changes during storage
• Surfactant degradation and particle formation

A conventional excipient package gives Alvotech and Teva a lower technical-risk pathway than a differentiated formulation using a new stabilizer or delivery technology.

Injection experience

Selarsdi is administered subcutaneously for psoriasis and psoriatic arthritis and after intravenous induction for inflammatory bowel disease. At the marketed concentrations, the excipient strategy must support acceptable viscosity, syringeability, injection force, and local tolerability.

The absence of a strong local anesthetic or complex viscosity modifier keeps the formulation simpler. Commercial differentiation therefore depends more on:

• Needle gauge
• Syringe glide force
• Injection volume
• Autoinjector integration
• Device ergonomics
• Storage and handling instructions

Supply reliability

Histidine, sucrose, polysorbate 80, and water for injection have established pharmaceutical supply chains. This supports scale-up and limits dependence on a single specialized excipient manufacturer.

Polysorbate 80 remains the most operationally sensitive component. Its quality can vary by source, and degradation may generate free fatty acids, particles, or peroxide-related stress that affects antibody stability. A robust commercial program needs tight controls on:

• Peroxide content
• Fatty-acid composition
• Hydrolysis products
• Lot-to-lot variability
• Container closure compatibility
• Long-term refrigerated stability

Patent exposure

The excipient package itself is unlikely to create a broad, standalone patent moat. The strategic value lies in formulation process know-how, impurity control, container closure selection, filling conditions, and any device or presentation patents.

What formulation patents protect Selarsdi or competing ustekinumab products?

Selarsdi is a biosimilar, so its commercial freedom-to-operate analysis includes both Stelara-related patent rights and Selarsdi-specific formulation or manufacturing claims.

Reference-product patent landscape

Stelara's original composition and use patents have largely expired or reached the end of their effective commercial life. The principal commercial issue has been later-filed patents relating to formulations, dosing, manufacturing, and methods of treatment.

Biologic patents do not appear in the FDA Orange Book in the same way as small-molecule drug patents. Relevant rights are identified through patent litigation, the Purple Book framework, FDA patent disclosures where applicable, and public court filings. [4]

Formulation patent categories

The relevant patent categories include:

1. Antibody concentration and stability
   Claims may cover specific concentrations, pH ranges, stabilizer ratios, surfactant levels, or storage conditions.

2. Polysorbate control
   Claims may address low-peroxide surfactant compositions, degradation control, or methods for reducing particles during storage.

3. Container closure systems
   Prefilled syringes, elastomeric components, silicone oil levels, and low-silicone systems may be protected separately from the drug formulation.

4. Manufacturing processes
   Claims may cover cell culture, purification, viral clearance, concentration, diafiltration, filling, or storage processes.

5. Delivery devices
   Autoinjectors, needle shields, syringe assemblies, and dose-delivery systems can create separate patent barriers.

6. Method-of-use patents
   Dosing regimens, patient populations, treatment sequencing, and maintenance schedules can remain relevant even when composition patents have expired.

Selarsdi's excipient composition is conventional enough that commercial defensibility is more likely to come from process controls, manufacturing scale, supply agreements, and device integration than from a new chemical formulation.

When does Stelara lose exclusivity, and what does that mean for Selarsdi?

Stelara's effective U.S. exclusivity has been extended through settlements between Johnson & Johnson's Janssen unit and biosimilar developers. Those agreements allowed biosimilar entry before the latest asserted patent expirations, subject to negotiated launch dates.

Alvotech and Teva announced a U.S. settlement with Janssen in 2023. The agreement permits Selarsdi to launch in the United States on or after February 21, 2025, subject to regulatory approval and settlement terms. [5]

Event	Date or status
Stelara FDA approval	2009
Selarsdi FDA approval	April 16, 2024
Selarsdi interchangeable designation	Granted with FDA approval
U.S. settlement with Janssen	Announced 2023
Permitted U.S. Selarsdi launch	February 21, 2025
Primary commercial erosion period	2025 onward

The launch date creates a defined commercial window. Selarsdi entered a market in which several ustekinumab biosimilars were expected to compete, making price, contracting, supply continuity, and pharmacy substitution more important than approval status alone.

Which companies are challenging Stelara?

The competitive ustekinumab biosimilar field includes several large pharmaceutical companies and specialist biosimilar developers.

Company	Product or program	Commercial relevance
Alvotech and Teva	Selarsdi, ustekinumab-aekn	FDA-approved interchangeable biosimilar
Amgen	Ustekinumab biosimilar program	Large-scale immunology commercial infrastructure
Celltrion	Ustekinumab biosimilar program	Established biosimilar and infliximab presence
Samsung Bioepis	Ustekinumab biosimilar program	Strong global biosimilar platform
Biocon Biologics	Ustekinumab biosimilar program	Broad immunology and biosimilar portfolio
Fresenius Kabi	Ustekinumab biosimilar program	Expanding U.S. biosimilar presence
Formycon partners	Ustekinumab development activity	European and global commercialization potential

The number of entrants creates two opposing effects. More competition accelerates price erosion and payer adoption. It also reduces the probability that one product can maintain a large price premium solely through interchangeability.

How does Selarsdi's interchangeable status affect generic substitution?

Selarsdi is not a generic drug. It is an interchangeable biosimilar under the Public Health Service Act.

Interchangeability can provide a pharmacy substitution advantage, but the commercial effect depends on:

• State substitution laws
• Payer formulary design
• Specialty-pharmacy contracts
• Provider prescribing behavior
• Patient support services
• Wholesaler inventory
• Net price after rebates
• Availability of competing ustekinumab biosimilars

For physician-administered or specialty-distributed products, payer controls can be more important than the FDA interchangeability designation. Health plans may prefer one biosimilar through preferred formulary placement, while hospitals and specialty pharmacies may use lowest-net-cost contracting.

What commercial opportunities exist for Selarsdi excipients?

1. Polysorbate 80 supply and quality control

The largest excipient-related opportunity is not a new ingredient. It is high-quality polysorbate 80 with improved control of oxidation, hydrolysis, particles, and fatty-acid variability.

Potential commercial products include:

• Low-peroxide polysorbate 80
• Pharmaceutical-grade material with tighter compositional limits
• Stabilized polysorbate 80 grades
• Single-use, ready-to-use excipient solutions
• Analytical packages for lot release and degradation monitoring

A supplier with validated low-variability polysorbate 80 could support Selarsdi and other antibody biosimilars using similar formulation systems.

2. Ready-to-use buffer systems

Prequalified histidine-histidine hydrochloride buffers can reduce development time and manufacturing variability. Opportunities include:

• Sterile-filterable histidine buffer concentrates
• Compendial-grade premixes
• Single-use buffer bags
• Custom pH-adjusted systems
• Low-endotoxin and low-particulate presentations

These products are valuable where biosimilar manufacturers seek faster scale-up without changing the final formulation.

3. Prefilled syringe and autoinjector components

The commercial value of excipient strategy extends into the primary container. Selarsdi's subcutaneous presentations require reliable compatibility among the protein, polysorbate 80, syringe materials, silicone oil, stopper, needle shield, and adhesive components.

Potential opportunities include:

• Low-silicone prefilled syringes
• Tungsten-controlled glass syringes
• Protein-compatible elastomers
• Low-extractables needle shields
• Autoinjector platforms for 90 mg maintenance doses
• Device systems with lower injection force

A device change may require additional comparability work but can improve patient acceptance and payer positioning.

4. Higher-concentration or lower-volume presentations

A lower-volume presentation can improve injection convenience and may support autoinjector use. The technical challenge is maintaining protein stability and acceptable viscosity at higher concentration.

Relevant development targets include:

• Reduced injection volume
• Lower injection force
• Improved syringeability after refrigeration
• Longer room-temperature excursion allowances
• Reduced injection-site discomfort

Any new concentration or device would need regulatory bridging and could create a separate patent opportunity if the formulation and delivery claims are sufficiently narrow and non-obvious.

5. Cold-chain and packaging optimization

Selarsdi is a refrigerated biologic. Packaging improvements that preserve product quality during distribution can reduce waste and expand specialty-pharmacy reach.

Commercial opportunities include:

• Validated temperature-monitoring systems
• Improved insulated shippers
• Reduced secondary packaging
• Reusable cold-chain containers
• Packaging that supports controlled room-temperature excursions
• Real-time excursion tracking

These products are operationally important because biologic loss from temperature excursions can erode the savings generated by biosimilar pricing.

What are the main patent and regulatory risks for Selarsdi?

Paragraph IV challenges

Paragraph IV certification is primarily a Hatch-Waxman mechanism for small-molecule ANDAs. Selarsdi proceeded through the biosimilar pathway rather than as a conventional generic. Its patent strategy therefore centers on the Biologics Price Competition and Innovation Act, patent-list exchange, litigation, settlement agreements, and launch licenses rather than a standard Orange Book Paragraph IV filing. [4]

Orange Book status

Selarsdi is not an Orange Book-listed small-molecule drug. The relevant FDA reference framework is the Purple Book for biological products. The absence of an Orange Book listing does not eliminate patent risk. It changes the mechanism through which patent rights are disclosed and challenged.

Biosimilar competition

The main threat is rapid price compression after multiple ustekinumab biosimilars enter the market. Selarsdi's interchangeable designation may help, but it will not prevent:

• Payer-preferred competitor selection
• Rebate competition
• Channel-specific discounting
• Switching programs
• Hospital and specialty-pharmacy tenders
• International reference-price pressure

Manufacturing and IP barriers

The strongest barriers may be manufacturing rather than excipient patents. Ustekinumab is a complex antibody requiring:

• High-yield mammalian cell culture
• Consistent glycosylation
• Validated purification
• Viral clearance
• Low aggregate levels
• Stable subcutaneous formulation
• Reliable fill-finish capacity

Process changes that affect glycosylation, charge variants, aggregation, or potency can create regulatory comparability risk. A competitor with a lower manufacturing cost and reliable supply can outperform a technically similar product even with no meaningful excipient difference.

How strong is Selarsdi's patent estate?

Selarsdi's direct excipient patent estate appears commercially weaker than a proprietary formulation platform because the marketed formulation uses established ingredients. Its defensibility is stronger in four areas:

Area	Strategic strength
FDA interchangeability	High commercial value, but not exclusive
Manufacturing process	Potentially high if supported by confidential know-how and process patents
Device and packaging	Moderate; depends on claim scope and commercial adoption
Excipient composition	Low to moderate; conventional ingredient system
Supply chain	High operational value but generally not a patent barrier
Clinical indications	Limited differentiation because biosimilar labeling tracks the reference product

The most durable advantage is likely cost-efficient production combined with reliable supply and payer contracting. Excipient patents alone are unlikely to sustain a premium.

What revenue exposure does Selarsdi address?

Stelara generated multibillion-dollar annual sales for Johnson & Johnson before biosimilar erosion. The largest exposure is in psoriasis, psoriatic arthritis, Crohn's disease, and ulcerative colitis. U.S. market value is particularly important because Stelara's U.S. pricing and specialty-pharmacy distribution created a large target for biosimilar entrants.

Selarsdi's revenue opportunity depends on:

• Share captured from Stelara
• Number of competing biosimilars
• Net selling price
• Payer access
• Interchangeable substitution
• Manufacturing capacity
• Launch timing
• Ability to serve both dermatology and gastroenterology channels

A broad indication label gives Selarsdi access to the full reference-product market, but it also increases the need for commercial coverage across different prescriber groups and distribution channels.

Key Takeaways

• Selarsdi is an FDA-approved interchangeable biosimilar to Stelara, marketed by Teva and developed with Alvotech.
• Its excipient system uses histidine, histidine hydrochloride, sucrose, polysorbate 80, and water for injection.
• The formulation is conventional and regulatory-efficient, but it is unlikely to create a large standalone patent moat.
• Polysorbate 80 quality, protein aggregation control, syringe compatibility, and cold-chain performance are the main excipient-related technical priorities.
• The U.S. launch date under the Janssen settlement was February 21, 2025.
• Commercial success depends on net price, payer access, supply reliability, pharmacy substitution, and device usability.
• The main competitive risk is rapid price erosion from multiple ustekinumab biosimilars.
• The most attractive adjacent opportunities are low-variability polysorbate 80, ready-to-use histidine buffers, low-silicone syringe systems, autoinjectors, and cold-chain packaging.

FAQs

Does Selarsdi contain the same excipients as Stelara?

Selarsdi uses a comparable conventional antibody formulation containing histidine, histidine hydrochloride, sucrose, polysorbate 80, and water for injection. Biosimilar formulations do not have to contain identical excipients, but differences cannot create clinically meaningful differences.

Can Selarsdi be automatically substituted for Stelara?

Selarsdi received FDA interchangeable-biosimilar status. Actual pharmacy substitution depends on state law, payer policy, prescribing instructions, and specialty-pharmacy procedures.

Is Selarsdi protected by Orange Book patents?

No. Selarsdi is a biologic and is addressed through the Purple Book and the BPCIA patent framework rather than the conventional Orange Book system used for small-molecule drugs.

What excipient is most likely to create stability problems in Selarsdi?

Polysorbate 80 is the most operationally sensitive excipient because oxidation, hydrolysis, fatty-acid variability, and particle formation can affect antibody stability.

Can a new Selarsdi formulation create a separate commercial opportunity?

Yes. Lower-volume injections, autoinjectors, improved syringeability, room-temperature handling, and low-silicone container systems could create commercial value, but each change would require regulatory comparability, device validation, and freedom-to-operate analysis.

References

1. U.S. Food and Drug Administration. (2024). SELARSDI (ustekinumab-aekn) injection, for subcutaneous or intravenous use: Prescribing information. FDA.

2. Teva Pharmaceuticals. (2024). Teva and Alvotech announce U.S. FDA approval of SELARSDI (ustekinumab-aekn), an interchangeable biosimilar to Stelara. Teva Pharmaceuticals.

3. U.S. Food and Drug Administration. (2024). Biosimilar product information: Ustekinumab-aekn. FDA.

4. U.S. Food and Drug Administration. (2024). Purple Book: Database of licensed biological products. FDA.

5. Alvotech. (2023). Alvotech and Teva announce settlement and license agreement with Janssen for AVT04 in the United States. Alvotech.