List of Excipients in Branded Drug ADMELOG

ADMELOG Excipient Strategy, Patent Position, and Commercial Opportunities

Last updated: September 24, 2026

Admelog is Sanofi’s insulin lispro product, approved in the United States in 2017 as a rapid-acting mealtime insulin. Its formulation uses a conventional insulin excipient system: metacresol for antimicrobial preservation, glycerol for tonicity, phosphate buffer for pH control, zinc for insulin hexamer stabilization, and water for injection. The core excipient composition has limited standalone differentiation value. The strongest commercial opportunities are in improved stability, alternative presentations, pump compatibility, lower-cost manufacturing, and follow-on insulin products with differentiated delivery systems. [1,2]

What is the Admelog formulation and which excipients does it contain?

Admelog contains insulin lispro at 100 units/mL. The US prescribing information identifies the following inactive ingredients:

Component	Approximate concentration per mL	Primary formulation function
Glycerol	16 mg	Tonicity and physical stability
Dibasic sodium phosphate dihydrate	1.88 mg	Buffering and pH control
Metacresol	3.15 mg	Antimicrobial preservation
Zinc oxide	0.0197 mg	Insulin association and stabilization
Water for injection	Quantity sufficient	Vehicle
Hydrochloric acid or sodium hydroxide	As required	pH adjustment

The finished product has a target pH in the range of approximately 7.0 to 7.8. Metacresol is the principal preservative. Zinc supports the formation and stabilization of insulin assemblies, while glycerol and phosphate help maintain an injectable solution suitable for vial and pen delivery. [1]

Why does Admelog use metacresol?

Metacresol permits multidose presentations by limiting microbial growth after repeated withdrawals or pen use. It is widely used in commercial insulin products, but it creates formulation and market constraints:

• Some patients have sensitivity or intolerance to phenolic preservatives.
• Metacresol can interact with container-closure systems and delivery devices.
• Concentration changes may affect insulin self-association, adsorption, and injection tolerability.
• Preservative reduction or removal may require a different presentation, sterile manufacturing strategy, or single-use format.

A preservative-free insulin lispro product could address a narrow clinical segment, but it would require a new stability and microbiological control strategy rather than a simple excipient substitution.

What role does zinc play in Admelog?

Zinc stabilizes insulin lispro in solution and influences the equilibrium between monomeric, dimeric, and hexameric forms. That balance affects absorption after subcutaneous injection. A commercial developer changing zinc concentration would need to evaluate:

• Chemical degradation and aggregation
• Injection-site tolerability
• Subcutaneous absorption
• Immunogenicity
• Compatibility with infusion pumps and tubing
• Container and device adsorption
• Comparability against Admelog and other insulin lispro products

Zinc is therefore a technically important excipient even though its concentration is low.

What dosage forms and delivery systems are protected by Admelog’s formulation strategy?

Admelog is marketed in a 10 mL vial and a 3 mL SoloStar prefilled pen presentation in the United States. The same active ingredient and general excipient system must support different use patterns, including repeated vial withdrawal, pen dosing, and storage through the in-use period. [1]

Vial and prefilled-pen opportunities

The principal commercial distinction between a vial and a pen is not the active ingredient. It is the delivery system, user interface, dosing accuracy, waste profile, and manufacturing economics.

Potential opportunities include:

1. Lower-cost disposable pens using simplified component counts.
2. Reusable pen systems with replaceable cartridges.
3. Connected pens that record dose and timing.
4. Smaller-volume pens for pediatric or low-dose users.
5. Device designs that reduce residual insulin and overfill.
6. Packaging optimized for emerging-market distribution.

Device patents may provide stronger practical protection than patents directed only to glycerol, metacresol, phosphate, or zinc concentrations.

Pump-compatible formulations

Admelog is labeled for use in certain continuous subcutaneous insulin infusion systems. Pump use creates additional requirements for chemical stability, occlusion resistance, reservoir compatibility, tubing adsorption, and prolonged exposure to elevated temperatures. [1]

A competing formulation could pursue differentiation through:

• Longer in-pump stability
• Reduced precipitation or aggregation
• Lower adsorption to polymer reservoirs
• Compatibility with automated insulin-delivery systems
• Improved stability during intermittent refrigeration
• Reduced sensitivity to agitation and air-liquid interfaces

These attributes could support device partnerships or licensing even if the formulation remains close to Admelog’s excipient profile.

What patents protect Admelog and its excipients?

The basic Admelog excipient system has limited patent strength because glycerol, phosphate, metacresol, zinc, and water are established pharmaceutical ingredients. A patent directed only to their presence is unlikely to provide durable protection absent a novel concentration range, interaction, stability result, delivery application, or manufacturing process.

The relevant protection categories are:

Protection category	Expected commercial value	Main vulnerability
Insulin lispro composition	Low for new entrants because the molecule is mature	Prior art and expiry of molecule-level rights
Conventional excipient combination	Low to medium	Extensive insulin formulation prior art
Narrow excipient ratios	Medium	Obviousness and design-around risk
Long-term stability formulation	Medium to high if data-supported	Requires credible unexpected results
Pump-compatible formulation	Medium to high	Device and use-around strategies
Pen or cartridge system	Medium to high	Separate device patent landscape
Manufacturing process	Medium	Trade-secret and process-replication issues
High-concentration insulin lispro	High if clinically and technically differentiated	Clinical, device, and regulatory burden
Preservative-free or low-preservative product	Medium	Microbiological and multidose-use constraints

A commercial freedom-to-operate analysis should separate patents covering insulin lispro, formulation parameters, containers, pen mechanisms, pump use, manufacturing, and methods of treating diabetes. A single Orange Book or Purple Book search is not sufficient to capture all relevant rights.

Are Admelog excipients independently patentable?

The ingredients themselves are not new. Potentially protectable subject matter may include:

• A defined ratio of glycerol, phosphate, zinc, and preservative
• A formulation with improved aggregation control
• A specified impurity profile
• A stability result under pump-use conditions
• A low-temperature or high-temperature storage profile
• A container-closure combination
• A method for reducing adsorption in infusion tubing
• A manufacturing sequence that improves batch consistency

The strongest claims would need measurable technical effects. Generic claims stating that insulin lispro is combined with conventional excipients would face substantial prior-art risk.

When did Admelog receive FDA approval and lose market exclusivity?

The FDA approved Admelog on December 11, 2017, under NDA 208751. The product was approved as a follow-on insulin lispro using the 505(b)(2) pathway. [2]

Insulin products approved under the drug provisions of the Federal Food, Drug, and Cosmetic Act transitioned to the biologics framework on March 23, 2020. The statutory transition changed the regulatory classification of insulin products, but it did not recreate molecule-level exclusivity for mature insulin lispro. [3]

Milestone	Date or status
FDA approval	December 11, 2017
Original regulatory pathway	505(b)(2) NDA
Active ingredient	Insulin lispro
Transition to biologics framework	March 23, 2020
Basic molecule opportunity	Mature and highly competitive
Principal remaining protection areas	Formulation, device, manufacturing, use, and trade secrets

Admelog’s commercial protection is therefore more dependent on manufacturing scale, formulary access, contracting, supply reliability, device economics, and regulatory execution than on a long remaining period of molecule exclusivity.

What is the Orange Book and regulatory status of Admelog?

Admelog was initially approved as an NDA product. FDA’s transition of insulin products into the biologics framework means that regulatory analysis must account for both the original NDA history and the post-2020 biologics regime. [2,3]

The key regulatory issues for competitors are:

• Whether the proposed product follows a 351(a) biologics license application pathway
• Whether it is evaluated as a biosimilar to insulin lispro
• Whether interchangeability is sought
• Whether the product uses the same or a different excipient system
• Whether a new delivery device requires separate bridging work
• Whether pump compatibility is included in the label
• Whether the product relies on a reference-product sponsor’s data

Does Admelog face Paragraph IV challenges?

Paragraph IV litigation is principally associated with abbreviated new drug applications and listed patents in the Orange Book. A conventional insulin lispro competitor may instead proceed through a biologics pathway after the insulin transition, depending on the product’s legal and regulatory structure.

The practical risk is therefore not limited to a Paragraph IV filing. A competitor may challenge relevant formulation or device patents through:

• An ANDA-based patent certification, if applicable
• A biosimilar application
• An inter partes review
• A declaratory-judgment action
• A non-infringement or invalidity defense after launch

No specific Paragraph IV dispute is identified in the FDA materials cited here. Patent litigation must be assessed patent by patent rather than inferred from Admelog’s approval route.

Which companies challenge Admelog commercially?

Admelog competes in a crowded rapid-acting insulin market:

Product	Sponsor	Active ingredient	Competitive position
Admelog	Sanofi	Insulin lispro	Follow-on lispro, vial and pen
Humalog	Eli Lilly	Insulin lispro	Originator lispro and major benchmark
Lyumjev	Eli Lilly	Insulin lispro	Faster-acting lispro formulation
NovoRapid/NovoLog	Novo Nordisk	Insulin aspart	Major rapid-acting insulin competitor
Fiasp	Novo Nordisk	Insulin aspart	Faster-acting aspart formulation
Apidra	Sanofi	Insulin glulisine	Sanofi’s other rapid-acting insulin

The main commercial threat is substitution among rapid-acting insulins rather than direct substitution only by Admelog-specific follow-on products. Payers can move utilization between insulin lispro, insulin aspart, and insulin glulisine based on rebates, net price, formulary placement, supply, and patient access.

What are the commercial opportunities in Admelog excipients?

1. Lower-cost follow-on insulin lispro

The most direct opportunity is a lower-cost insulin lispro with a conventional excipient system. The product would compete on:

• Net price
• Payer contracting
• Manufacturing yield
• Fill-finish cost
• Pen economics
• Supply reliability
• Interchangeability strategy

Because the basic formulation is familiar, the main barriers are regulatory comparability and commercial scale.

2. Improved high-temperature stability

Insulin distribution in tropical and resource-constrained markets creates demand for products with better stability outside refrigerated conditions. A formulation that maintains potency and limits aggregation under defined temperature excursions could support differentiated labeling and distribution economics.

Potential claim themes include:

• Stabilizer combinations
• Reduced aggregation after temperature cycling
• Improved in-use stability
• Container-closure systems with lower oxygen or moisture ingress
• Refrigeration-free or reduced-refrigeration storage periods

The regulatory value depends on whether the stability improvement supports a meaningful label change.

3. Pump-optimized insulin lispro

A formulation designed for extended pump residence could support licensing to pump manufacturers and automated insulin-delivery companies. The opportunity is technically attractive because pump users face repeated exposure to heat, agitation, tubing surfaces, and reservoir materials.

The product would need evidence of chemical and physical stability in representative pumps, reservoirs, and infusion sets.

4. Pediatric and low-dose delivery

A pen with half-unit dosing, lower dead volume, or improved dose accuracy could target children, older patients, and insulin-sensitive users. Device claims may be more defensible than claims to conventional excipients.

5. Preservative-reduced or preservative-free presentations

This is a narrower opportunity. It could target patients with preservative intolerance or specific clinical needs. The commercial case depends on whether the product can maintain sterility and stability without sacrificing multidose convenience.

6. Combination with digital adherence tools

Dose-recording pens and connected diabetes platforms can create commercial differentiation without materially changing the insulin formulation. Licensing opportunities may arise with device companies, diabetes software providers, and pharmacy-channel distributors.

How strong is the Admelog patent estate?

The formulation patent estate is best characterized as moderate to weak for conventional excipient claims and potentially stronger for specific delivery, stability, device, and manufacturing claims.

Factor	Assessment
Molecule-level exclusivity	Weak because insulin lispro is mature
Conventional excipient protection	Weak unless claims are unusually narrow and technically supported
Stability claims	Moderate where supported by comparative data
Pump-use claims	Moderate, with meaningful technical barriers
Pen and device claims	Moderate to strong depending on claim scope
Manufacturing know-how	Potentially strong as trade secret
Commercial defensibility	More dependent on price, access, and supply than patents

The highest-value assets may not be publicly visible patents. Batch controls, cell-bank processes, purification methods, aggregation limits, fill-finish parameters, and supplier qualification can create practical barriers that are difficult to replicate quickly.

What licensing deals and partnership opportunities exist?

The cited FDA and product documents do not identify a major public excipient-platform license specific to Admelog. The most plausible partnership areas are:

• Insulin lispro biosimilar development
• Pen and cartridge technology
• Pump-compatible formulation development
• Connected dosing devices
• Cold-chain reduction
• Regional manufacturing and fill-finish
• Diabetes distribution and payer access

A technology owner with a validated stability improvement could license the formulation to a biologics manufacturer while retaining rights to the device or geographic markets.

What generic launch scenarios create risk for Admelog?

Scenario 1: Conventional lower-cost lispro

This is the highest-probability competitive scenario. It would exert pressure on Admelog through payer tenders and pharmacy substitution. Differentiation would depend on regulatory designation, price, and supply.

Scenario 2: Biosimilar or interchangeable lispro

An interchangeable product could create stronger substitution pressure if it secures favorable payer treatment and broad pharmacy availability. The commercial impact would depend on the product’s designation and state substitution rules.

Scenario 3: Faster-acting or pump-optimized lispro

This product would compete through clinical and delivery attributes rather than price alone. It could take share in automated insulin delivery and high-frequency pump use.

Scenario 4: Device-led entry

A competitor could retain a conventional lispro formulation while using a lower-cost or connected pen to gain access. This would reduce the value of formulation differentiation.

Key Takeaways

• Admelog uses a conventional insulin lispro excipient system built around glycerol, phosphate buffer, metacresol, zinc, and water.
• The ingredients are established and provide limited standalone patent leverage.
• The strongest protectable opportunities are formulation ratios with demonstrated stability benefits, pump compatibility, high-temperature stability, device integration, and manufacturing processes.
• Admelog was approved by FDA in 2017 under NDA 208751 and entered a biologics-centered regulatory environment after the 2020 insulin transition.
• Commercial pressure comes from Humalog, Lyumjev, NovoLog, Fiasp, Apidra, and potential biosimilar or follow-on insulin lispro entrants.
• Lower-cost manufacturing, payer contracting, pen economics, and supply reliability may be more important than conventional excipient patents.
• A differentiated excipient strategy should target a measurable product advantage, such as longer pump stability, reduced aggregation, improved temperature tolerance, or preservative reduction.

FAQs

Can a competitor copy Admelog’s excipients?

A competitor can use the same established excipients if it satisfies regulatory, quality, and intellectual-property requirements. The commercial challenge is proving product comparability and avoiding claims directed to specific ratios, stability results, devices, or manufacturing processes.

Is Admelog a biosimilar to Humalog?

Admelog was approved in 2017 as a 505(b)(2) follow-on insulin lispro product. Its regulatory history predates the 2020 transition of insulin products into the biologics framework. The term “biosimilar” should be applied based on the relevant FDA approval pathway and product designation, not solely on molecular identity.

What excipient could improve insulin lispro stability?

No single excipient guarantees improved stability. The most credible development paths involve optimizing zinc, buffering, tonicity, preservative concentration, container materials, and surfactant or stabilizer systems together, followed by aggregation, potency, pump, and immunogenicity testing.

Is a preservative-free Admelog alternative commercially attractive?

It could address a focused patient segment, but the product would face multidose sterility, in-use stability, packaging, and cost constraints. A preservative-free product is more commercially plausible in a single-use or specialized delivery system than as a direct replacement for a multidose vial.

What is the best IP strategy for a new insulin lispro product?

The strongest strategy combines formulation claims with device, pump-use, stability, manufacturing, and container-closure claims. Trade-secret protection for process controls and manufacturing know-how should complement public patent filings.

References

1. Sanofi-Aventis U.S. LLC. (2024). Admelog (insulin lispro injection) prescribing information. U.S. Food and Drug Administration.

2. U.S. Food and Drug Administration. (2017, December 11). Approval letter for Admelog, NDA 208751. Center for Drug Evaluation and Research.

3. U.S. Food and Drug Administration. (2020). Transition plan for insulin and other biological products approved under the Federal Food, Drug, and Cosmetic Act. U.S. Department of Health and Human Services.