List of Excipients in Branded Drug INSULIN DEGLUDEC

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Last updated: September 29, 2026

Insulin degludec has a concentrated excipient opportunity around formulation control rather than simple ingredient substitution. The commercial product, Tresiba, depends on phenol, metacresol, zinc, glycerol, and pH control to maintain a stable multihexamer depot after subcutaneous injection. Suppliers that can provide highly controlled excipient quality, low extractables, global regulatory support, and device-compatible packaging have the strongest entry opportunities. Biosimilar and follow-on insulin developers also need excipient strategies that preserve potency, aggregation limits, immunogenicity, injection performance, and shelf life.

Insulin Degludec Excipient Strategy and Commercial Opportunities

What excipients are used in insulin degludec formulations?

Insulin degludec is formulated in Tresiba as a sterile aqueous solution at U-100 and U-200 concentrations. The excipient system supports zinc-mediated insulin association, preservative protection, isotonicity, pH control, and chemical stability.

Component	Function in formulation	Strategic relevance
Phenol	Preservative and structural modulator	Influences insulin association and dissociation behavior
Metacresol	Preservative and protein-stabilizing excipient	Requires tight control of purity, concentration, and extractables
Glycerol	Tonicity agent and stabilizer	Affects osmolality, viscosity, and injection characteristics
Zinc	Promotes insulin hexamer and multihexamer formation	Critical to the prolonged absorption profile
Hydrochloric acid	pH adjustment	Controls molecular stability and preservative performance
Sodium hydroxide	pH adjustment	Supports batch-to-batch pH control
Water for injection	Vehicle	Must meet parenteral water and bioburden requirements

The commercial Tresiba label identifies insulin degludec, glycerol, metacresol, phenol, zinc, hydrochloric acid, sodium hydroxide, and water for injection as formulation components. Tresiba U-100 contains 100 units/mL, while Tresiba U-200 contains 200 units/mL. The products use the same active ingredient and a related excipient platform, but the higher concentration creates greater demands on viscosity, aggregation control, dose accuracy, and device compatibility (FDA, 2023a).

Ryzodeg, which combines insulin degludec with insulin aspart, uses a related insulin formulation platform. Its excipient strategy must support two active proteins with different absorption and stability requirements, making it a more complex target for follow-on development (FDA, 2023b).

How does the insulin degludec excipient system work?

The core technical function is controlled self-association of insulin degludec. In the pharmaceutical cartridge, insulin degludec forms multihexamer structures in the presence of zinc. After injection, phenol diffuses away, the multihexamer structure changes, and insulin monomers are gradually released for absorption.

This mechanism creates a direct link between excipient composition and pharmacokinetics. A change in zinc level, phenol concentration, metacresol concentration, pH, or ionic environment can alter:

• Hexamer and multihexamer formation
• Dissociation rate after injection
• Soluble aggregate levels
• Subvisible particle formation
• Chemical degradation
• Local tolerability
• Dose-to-dose delivery consistency
• Exposure and glucose-lowering duration

The excipient system therefore has a higher technical barrier than a conventional aqueous peptide formulation. A follow-on product cannot treat excipients as passive ingredients. It must demonstrate that changes do not materially alter the product’s quality attributes or clinical performance.

Why zinc is commercially important

Zinc is central to the degludec depot mechanism. Its concentration, chemical form, purity, and interaction with the insulin protein require close control. Potential supplier value exists in pharmaceutical-grade zinc chloride or another validated zinc source with:

• Low heavy-metal contamination
• Consistent elemental assay
• Low insoluble matter
• Controlled chloride content
• Parenteral-grade documentation
• Reliable global supply

Zinc is also a potential source of manufacturing variability. Small deviations can affect association state, particle profile, and release behavior. A supplier with strong trace-metal analytics and lot-to-lot control can compete on performance assurance rather than commodity price.

Why phenol and metacresol require separate strategies

Phenol and metacresol are both preservatives, but they also influence insulin structure. Their commercial value is therefore tied to impurity control and functional consistency.

Key specifications include:

• Assay and related organic impurities
• Residual solvents
• Oxidation products
• Color and clarity
• Trace metals
• Microbial quality
• Container-closure compatibility

Preservative suppliers can differentiate through low-impurity grades, validated sterilization or bioburden controls, regional regulatory files, and supply continuity. The opportunity is stronger for suppliers that can support a complete qualification package, including extractables and leachables data for cartridges, pens, and filling equipment.

What formulation patents protect insulin degludec?

Insulin degludec is protected through a combination of active-ingredient, formulation, manufacturing, delivery, and method-of-use rights. The most relevant patent categories include:

Patent category	Protected subject matter	Commercial impact
Active ingredient	Modified insulin sequence and chemical structure	Protects the degludec molecule
Formulation	Zinc-containing insulin solutions with preservatives and stabilizers	Can limit alternative excipient systems
Concentration	U-100 and U-200 presentations	May affect high-concentration follow-on products
Manufacturing	Recombinant production, purification, crystallization, and formulation processes	Can create process-development barriers
Delivery device	Prefilled pens, cartridges, dose mechanisms, and reservoir systems	Can delay device-compatible launches
Method of use	Basal insulin treatment and dosing regimens	May affect labeling and substitution strategy
Combination products	Insulin degludec with insulin aspart in Ryzodeg	Creates a separate combination-product estate

The formulation estate is commercially important because degludec’s long duration depends on excipient-mediated self-association. A competitor may avoid a specific formulation claim by changing preservative ratios or using a different stabilizer, but the change must still produce a clinically comparable product.

A formulation design-around is not automatically a commercial design-around. The alternative must meet stability, potency, immunogenicity, device, and regulatory requirements. A product with a legally distinct excipient system may still require extensive development if the change affects pharmacokinetics or injection performance.

What is the FDA regulatory status of insulin degludec?

Tresiba was approved by the FDA as a once-daily basal insulin for adults and pediatric patients with diabetes. It is available in U-100 and U-200 strengths. The product is marketed by Novo Nordisk (FDA, 2023a).

Insulin products occupy a special regulatory position. FDA insulin products historically approved under the Federal Food, Drug, and Cosmetic Act transitioned to the Public Health Service Act biologics framework in 2020. Follow-on developers generally evaluate the 351(k) biosimilar pathway rather than an ordinary small-molecule ANDA pathway.

Regulatory issue	Insulin degludec implication
Active ingredient	Recombinant therapeutic protein
Primary competition pathway	Biosimilar or follow-on biologic pathway
Ordinary generic substitution	Not equivalent to a conventional small-molecule generic
Reference product	Tresiba
FDA reference tools	Purple Book and Drugs@FDA
Interchangeability	Requires separate FDA designation and evidence
Formulation changes	Must be assessed for analytical and clinical impact

A follow-on product must establish a high degree of similarity to the reference product. The analytical package typically addresses primary structure, higher-order structure, purity, aggregates, charge variants, potency, receptor binding, forced degradation, and immunogenicity risk. Excipients can materially affect these results and must be included in comparability planning.

Is insulin degludec listed in the Orange Book?

The Orange Book is primarily associated with approved small-molecule drug products and their patent and exclusivity listings. For biological products, the Purple Book is the more relevant FDA reference for biosimilar and interchangeability status.

The regulatory distinction matters commercially:

• A conventional ANDA is generally not the expected route for insulin degludec.
• Biosimilar applicants assess the reference biological product and any relevant exclusivity.
• Patent and licensing analysis must cover FDA listings, USPTO records, court dockets, and product-specific agreements.
• Device patents and formulation claims may remain relevant even when a biosimilar pathway is available.

A company pursuing degludec should separate FDA substitution status from patent freedom to operate. FDA approval does not eliminate infringement risk, and patent expiry does not guarantee automatic pharmacy substitution.

When does insulin degludec lose exclusivity?

Insulin degludec exclusivity is determined by several overlapping rights rather than a single date. Relevant periods may include:

1. Regulatory exclusivity for the reference product.
2. Patents covering the degludec molecule.
3. Formulation patents covering zinc, preservatives, concentration, or stability.
4. Manufacturing patents.
5. Pen and cartridge patents.
6. Method-of-use patents.
7. Patent settlements or licenses.
8. Pediatric exclusivity or other statutory extensions.

A commercial launch analysis must distinguish between the earliest legally permissible biosimilar approval date and the earliest practical market-entry date. A biosimilar may be approved before a full commercial launch if litigation, settlement terms, manufacturing readiness, device clearance, or interchangeability strategy affects timing.

Exact patent expiration and litigation conclusions require a current, product-specific review of FDA, USPTO, Patent Trial and Appeal Board, and federal court records. The relevant risk is likely to be distributed across formulation, delivery, and manufacturing claims rather than limited to the active ingredient alone.

What excipient opportunities exist for generic and biosimilar insulin degludec?

1. High-purity preservative supply

Phenol and metacresol are attractive supply opportunities because the required quality is higher than standard industrial-grade material. Suppliers can compete through:

• GMP manufacturing
• Regional dual sourcing
• Low extractables packaging
• Parenteral documentation
• Stable impurity profiles
• Long-term supply agreements
• Regulatory support for biosimilar dossiers

A supplier with a Drug Master File or equivalent technical package may reduce customer qualification time.

2. Zinc and trace-metal control

Zinc suppliers can offer value through high assay consistency and trace-metal control. Analytical methods should support elemental impurities, insoluble particles, and batch uniformity. Zinc supply can become a critical raw-material risk if only one qualified source is available.

3. Pharmaceutical glycerol

Glycerol is more commoditized, but injectable-grade glycerol still requires reliable control of purity, diethylene glycol and ethylene glycol contamination, water content, and microbial quality. Suppliers with global pharmacopeial compliance and validated logistics can capture volume in high-throughput insulin manufacturing.

4. Alternative stabilizer systems

Novel stabilizer systems may reduce dependence on phenol or metacresol, improve container compatibility, or expand room-temperature stability. Candidate approaches could include carefully selected amino acids, polyols, surfactants, or buffering systems.

The technical hurdle is high. A substitute must preserve degludec association behavior without increasing aggregation, injection-site reactions, viscosity, or immunogenicity. Any major excipient change can also increase the regulatory burden for a biosimilar developer.

5. Device and container-closure compatibility

Insulin degludec is sold in prefilled pen systems and cartridges. Excipient selection must account for interaction with:

• Glass or polymer reservoirs
• Elastomeric plunger components
• Needle interfaces
• Lubricants
• Silicone oil
• Adhesives
• Metal dose components

Preservatives and proteins can interact with container materials. Extractables and leachables, adsorption, visible particles, and dose-delivery force should be assessed during formulation screening rather than after the formulation is fixed.

How does U-200 insulin degludec change the commercial opportunity?

U-200 degludec provides a lower injection volume for patients requiring higher basal doses. The higher concentration creates a differentiated formulation and device opportunity.

Critical U-200 attributes include:

• Protein concentration
• Viscosity
• Osmolality
• Dose accuracy
• Pen-force performance
• Aggregation under storage and transport
• Cartridge filling accuracy
• Needle compatibility
• Human-factors performance

A U-200 follow-on product may require more than a simple twofold concentration adjustment. The product must demonstrate consistent delivery through the intended device and preserve the reference product’s quality profile. Suppliers that provide low-shear filling systems, compatible primary packaging, and particle-control technologies can target this segment.

What manufacturing and intellectual-property barriers affect insulin degludec?

The main barriers are biological production, analytical comparability, formulation control, device integration, and patent clearance.

Manufacturing barriers

Insulin degludec manufacturing requires control of recombinant expression, precursor processing, purification, chemical modification, folding, and final formulation. Process changes can affect impurities and higher-order structure. A follow-on manufacturer must develop a process that produces a highly similar product without copying protected manufacturing steps.

Analytical barriers

Routine insulin assays are insufficient for a full biosimilar package. Developers need orthogonal methods for:

• Molecular mass
• Sequence confirmation
• Disulfide connectivity
• Aggregates
• Particles
• Charge variants
• Potency
• Receptor binding
• Zinc association
• Preservative content
• Stability-indicating degradation

Intellectual-property barriers

Formulation and device patents can remain commercially significant after core molecule claims expire. The strongest competitive position may come from a product that uses a distinct excipient system, a non-infringing pen, and a manufacturing process with independent patent clearance.

Which companies are positioned to challenge insulin degludec?

Novo Nordisk remains the reference-product sponsor and incumbent supplier. Potential challengers include:

• Large insulin manufacturers with recombinant protein capacity
• Biosimilar specialists
• Contract development and manufacturing organizations
• Regional insulin producers
• Device companies partnering with biosimilar developers
• Excipient suppliers seeking preferred-vendor status

Competition is likely to develop through partnerships. A biosimilar company may license the active ingredient process, outsource formulation and fill-finish, and source the pen from a separate device manufacturer. This structure increases the importance of supply agreements, quality agreements, change-control rights, and patent indemnification.

No established FDA-approved biosimilar to insulin degludec should be assumed without confirmation from current FDA records. The commercial field remains less developed than the insulin glargine and insulin lispro follow-on markets.

What is the revenue opportunity for insulin degludec excipient suppliers?

The largest opportunity is not the unit price of glycerol or pH adjusters. It is qualification into a regulated, high-volume insulin platform.

Commercial value can come from:

• Multi-year supply contracts
• Dual-source qualification
• Regional manufacturing
• Excipient technical files
• Stability and compatibility data
• Analytical method support
• Supply-chain security
• Participation in biosimilar development programs
• Cross-selling into other peptide and insulin products

Preservatives and zinc offer higher technical differentiation than glycerol. Container-closure and device compatibility may offer the strongest margin potential because these services require specialized data and are harder to replace after approval.

How strong is the insulin degludec patent and formulation estate?

The estate is strategically meaningful because the product’s pharmacology is linked to formulation behavior. A competitor must address three distinct risks:

1. The active molecule and its production.
2. The excipient-mediated multihexamer system.
3. The pen, cartridge, and dosing presentation.

The formulation estate is strongest where claims define the combination of insulin degludec concentration, zinc level, preservatives, pH, and stability performance. Process patents may be more vulnerable to independent manufacturing routes, while device patents can be addressed through alternative pen designs.

A high-quality freedom-to-operate program should map each patent family by claim type, jurisdiction, terminal disclaimer, continuation status, prosecution history, and remaining term. Settlement agreements could also impose launch restrictions that are not apparent from patent expiry dates alone.

Key Takeaways

• Insulin degludec depends on zinc, phenol, metacresol, glycerol, and pH control for its formulation and prolonged absorption mechanism.
• Zinc and preservatives are the most technically differentiated excipient opportunities.
• U-200 products create added demand for viscosity control, device compatibility, and dose-delivery validation.
• Biosimilar competition is more relevant than a conventional ANDA generic pathway.
• The Purple Book and biologics framework are more relevant than a purely Orange Book-centered analysis.
• Formulation, manufacturing, and device patents can remain important after active-ingredient protection declines.
• Excipient suppliers can create the most value through qualification support, regulatory documentation, supply continuity, and compatibility data.
• No product strategy should treat excipients as interchangeable commodities.

FAQs

What is the most important excipient in insulin degludec?

Zinc is among the most important because it supports the multihexamer structure responsible for delayed insulin release. Phenol and metacresol also have structural effects beyond preservative activity.

Can phenol or metacresol be removed from an insulin degludec formulation?

Removal is technically possible only if another system preserves sterility, protein stability, association behavior, injection tolerability, and product shelf life. A major preservative change would require substantial comparability and regulatory support.

Is insulin degludec suitable for a conventional generic drug application?

Insulin degludec is a recombinant protein, so a biosimilar or follow-on biologic strategy is generally more relevant than a standard small-molecule ANDA.

Does a different excipient system avoid insulin degludec patent risk?

Not necessarily. A changed excipient system may avoid one formulation claim while remaining exposed to active-ingredient, manufacturing, device, or method-of-use patents.

Which excipient has the best commercial margin potential?

Specialty-grade phenol, metacresol, and zinc generally offer more differentiation than glycerol or pH adjusters. Compatibility testing, regulatory documentation, and supply assurance can create higher margins than raw-material sales alone.

References

1. Food and Drug Administration. (2023a). Tresiba insulin degludec injection prescribing information. U.S. Department of Health and Human Services.

2. Food and Drug Administration. (2023b). Ryzodeg insulin degludec and insulin aspart injection prescribing information. U.S. Department of Health and Human Services.

3. Food and Drug Administration. (2020). Transition of insulin products and other biological products to the biologics license application pathway. U.S. Department of Health and Human Services.

4. Food and Drug Administration. (2024). Purple Book: Database of licensed biological products. U.S. Department of Health and Human Services.

5. European Medicines Agency. (2013). Tresiba: EPAR product information. European Union.