List of Excipients in Branded Drug KISUNLA

KISUNLA Excipient Strategy and Commercial Opportunities for Donanemab

Last updated: August 14, 2026

KISUNLA, Eli Lilly’s donanemab-azbt, is an intravenous monoclonal antibody approved by the FDA for adults with early symptomatic Alzheimer’s disease, including mild cognitive impairment and mild dementia with confirmed amyloid pathology. Its commercial excipient opportunity is concentrated in biologics-grade raw materials, polysorbate control, container-closure systems, infusion compatibility, analytical testing, and future subcutaneous or higher-concentration presentations.

The current formulation uses a conventional liquid monoclonal-antibody platform. The strongest commercial opportunities are therefore not replacement of a single inactive ingredient, but improvements in stability, oxidation control, particulate reduction, shelf life, manufacturing yield, and delivery convenience.

What excipients are in KISUNLA?

KISUNLA is supplied as a sterile, preservative-free intravenous solution containing donanemab-azbt at 17.5 mg/mL. The approved product is packaged in a single-dose vial and diluted before intravenous infusion.

Component	Function in the formulation	Commercial relevance
Donanemab-azbt	Active antibody	Requires control of aggregation, fragmentation, oxidation, charge variants, and particles
Histidine	Buffer	Controls formulation pH and antibody stability
Histidine hydrochloride monohydrate	Buffer component	Establishes buffer capacity and pH control
Sodium chloride	Tonicity agent	Supports physiological osmolality
Polysorbate 80	Surfactant	Reduces interfacial stress and adsorption to equipment and containers
Water for injection	Vehicle	Requires pharmaceutical-grade quality and validated bioburden and endotoxin control

The FDA prescribing information identifies histidine, histidine hydrochloride monohydrate, sodium chloride, polysorbate 80, and water for injection as inactive ingredients in KISUNLA.[1]

How does KISUNLA’s formulation compare with other Alzheimer’s antibodies?

KISUNLA uses an excipient architecture similar to other commercially approved anti-amyloid antibodies. The primary formulation variables are the buffer system, surfactant identity and concentration, tonicity, protein concentration, and container-closure configuration.

Product	Active ingredient	Administration	Formulation implications
KISUNLA	Donanemab-azbt	Intravenous infusion	Liquid antibody formulation with histidine buffer and polysorbate 80
LEQEMBI	Lecanemab-irmb	Intravenous infusion	Requires comparable control of aggregation, particles, and infusion compatibility
ADUHELM	Aducanumab-avwa	Intravenous infusion	Similar biologic formulation and delivery constraints
Future anti-amyloid products	Various antibodies	Intravenous or subcutaneous	May create demand for higher-concentration, low-viscosity and low-volume formulations

The direct competitive issue is delivery burden. KISUNLA is administered by intravenous infusion, with dosing intervals that can extend after amyloid plaque clearance. A formulation that enables subcutaneous administration, shorter infusion time, or lower preparation complexity could have commercial value even if the active antibody remains unchanged.

What excipient risks affect KISUNLA manufacturing?

Polysorbate 80 is the highest-priority excipient risk in the current formulation. It can undergo hydrolysis and oxidation, generating degradation products that may correlate with protein oxidation, subvisible particles, or reduced physical stability. Risk depends on supplier grade, impurity profile, storage conditions, oxygen exposure, container interaction, and manufacturing shear.

Polysorbate 80 supply and quality

Commercial suppliers can compete on:

• Low-peroxide and low-aldehyde profiles
• Defined fatty-acid composition
• Lot-to-lot consistency
• Oxidative stability
• Control of hydrolysis products
• Extractables and leachables data
• Biologics-specific regulatory documentation
• Global supply continuity

KISUNLA suppliers should not treat polysorbate 80 as a commodity excipient. The relevant purchasing decision includes analytical support, change-control history, impurity characterization, and comparability data after supplier or process changes.

Histidine buffer supply

Histidine and histidine hydrochloride monohydrate are lower-risk materials from a supply perspective, but they remain important for pH control and antibody stability. Commercial opportunities include:

• High-purity biologics grades
• Low-metal specifications
• Consistent endotoxin and bioburden control
• Validated manufacturing changes
• Regional dual sourcing
• Ready-to-use buffer concentrates

The strongest value proposition is regulatory continuity rather than simple price reduction. A supplier change affecting pH, conductivity, trace metals, or buffer impurity levels could trigger comparability work.

Sodium chloride and water for injection

Sodium chloride is widely available and unlikely to create differentiated commercial value by itself. Water for injection, however, remains critical at the manufacturing-site level because microbial, endotoxin, conductivity, and total organic carbon controls can affect batch release and facility qualification.

What formulation patents could protect KISUNLA?

Potential KISUNLA-related formulation patents could cover the following subject matter:

1. Donanemab concentrations and pH ranges.
2. Histidine buffer concentration and ratio of histidine to histidine hydrochloride.
3. Polysorbate 80 concentration or impurity limits.
4. Reduced aggregation or oxidation during storage.
5. Long-term stability in a liquid formulation.
6. Compatibility with vial, stopper, syringe, infusion bag, or tubing materials.
7. Dilution conditions for intravenous administration.
8. Freeze-thaw stability.
9. High-concentration formulations for subcutaneous delivery.
10. Lyophilized or reconstitutable donanemab formulations.
11. Device-assisted administration.
12. Methods for reducing infusion-related reactions or preparation time.

A formulation patent must provide more than a list of standard excipients. The commercial strength of a claim generally depends on whether the patent links a defined composition to a measurable technical effect, such as reduced high-molecular-weight species, lower particle formation, improved recovery after dilution, or extended shelf life.

Publicly available product labeling confirms the approved formulation components but does not by itself establish the scope of Eli Lilly’s unpublished, pending, or non-Orange-Book patent claims. As a monoclonal antibody, donanemab is generally evaluated through the biologics patent framework and the FDA Purple Book rather than the small-molecule Orange Book.[2]

When does KISUNLA lose regulatory exclusivity?

KISUNLA was approved on July 2, 2024.[3] Donanemab-azbt is a biologic, so the principal statutory reference-product exclusivity period is 12 years from first licensure under the Biologics Price Competition and Innovation Act, subject to statutory rules and any applicable pediatric extension.[4]

Event	Date or timing
FDA approval	July 2, 2024
Reference-product exclusivity framework	12 years from first licensure
Earliest standard biosimilar licensure timing	Generally linked to the 12-year reference-product exclusivity period
Patent expiry	Depends on issued claims, patent-term adjustment, terminal disclaimers, and any litigation outcome
Pediatric extension	Potential six-month extension if statutory requirements are met

The 12-year period does not mean that all patent barriers end at the same time. Biosimilar applicants may conduct development and submit an application under the BPCIA framework before commercial launch, while patents can delay or prevent market entry beyond regulatory exclusivity.

Is KISUNLA listed in the Orange Book?

No. KISUNLA is a biologic, and its biologic patent and exclusivity information is generally associated with the FDA Purple Book rather than the Orange Book.[2] The Orange Book is primarily used for approved drug products regulated under the Federal Food, Drug, and Cosmetic Act and for associated patent certifications, including Paragraph IV certifications.

For KISUNLA, the relevant competitive pathway is a biosimilar application under section 351(k) of the Public Health Service Act. A biosimilar applicant may challenge relevant patents through the BPCIA patent-exchange process and subsequent litigation.

Which companies could challenge KISUNLA?

Potential challengers include large biosimilar developers with monoclonal-antibody manufacturing capacity, global clinical infrastructure, and experience in FDA 351(k) submissions. No company should be characterized as a confirmed KISUNLA challenger without a public filing, patent notice, litigation complaint, or regulatory disclosure.

The most credible commercial challengers would need to address:

• Analytical similarity to donanemab-azbt
• Glycosylation and charge-variant comparability
• Aggregation and particle profiles
• Immunogenicity
• Infusion compatibility
• Clinical or pharmacodynamic requirements imposed by FDA
• Manufacturing scale and cost
• Interchangeability strategy, if pursued
• Patent litigation and settlement exposure

Unlike a conventional generic, a donanemab biosimilar competitor cannot rely solely on identical excipients and dose strength. The product must demonstrate a high degree of similarity to the reference biologic, with no clinically meaningful differences in safety, purity, and potency.

What generic or biosimilar launch risks exist for KISUNLA?

The near-term generic launch risk is low because KISUNLA is a biologic and received approval in 2024. The material long-term risk is biosimilar competition after reference-product exclusivity and patent barriers are addressed.

Risk categories

Risk	Likely impact
Biosimilar entry after regulatory exclusivity	Price pressure and contracting concessions
Formulation patent litigation	Delayed launch or settlement-linked entry
Manufacturing patents	Limits on process design and scale-up
Subcutaneous reformulation	Could shift demand away from the current intravenous product
Competing Alzheimer’s antibodies	Reduces share without requiring biosimilar entry
Payer restrictions	Affects treatment initiation and product selection
Safety monitoring requirements	May limit prescribing and increase administration cost
Raw-material shortages	Can affect production continuity and inventory levels

Biosimilar risk is also affected by market size. The treatment population depends on amyloid confirmation, disease stage, MRI monitoring, infusion capacity, and reimbursement. A smaller realized market can reduce the incentive for early biosimilar entry even when the legal pathway is available.

What commercial opportunities exist in KISUNLA excipients?

1. Low-degradation polysorbate 80

The highest-value opportunity is a biologics-grade polysorbate 80 with validated control of peroxide, aldehyde, free fatty acid, and hydrolysis products. Suppliers that provide stability-indicating data and change-control support can compete for qualification in Lilly’s supply chain and in biosimilar programs.

2. Alternative surfactants

Poloxamer 188 and other nonionic surfactants could be evaluated as alternatives or complements to polysorbate 80. The commercial barrier is technical comparability. An alternative must preserve antibody potency and minimize aggregation, adsorption, particles, and immunogenicity risk.

A successful alternative-surfactant program could support a formulation patent if it demonstrates a non-obvious stability advantage in a defined donanemab composition.

3. High-concentration formulations

A higher-concentration formulation could reduce infusion volume or support subcutaneous injection. The main constraints are viscosity, protein-protein interaction, injection force, device compatibility, and local tolerability.

This is a higher-value but higher-risk opportunity than commodity excipient supply. It may require a new formulation, new device, new clinical bridging strategy, and separate patent protection.

4. Container-closure systems

Commercial opportunities include:

• Low-binding glass vials
• Elastomeric stoppers with reduced extractables
• Prefilled syringes
• Cartridge systems
• Low-silicone or silicone-controlled components
• Infusion bags and tubing with lower protein adsorption
• Container systems optimized for low fill-volume losses

Container-closure changes can affect visible and subvisible particles, antibody recovery, and stability. They may also create device or combination-product IP.

5. Ready-to-use dilution systems

KISUNLA is diluted before administration. Ready-to-use bags, standardized dilution kits, or closed-system transfer devices could reduce preparation errors and occupational handling burden. These products may gain adoption through hospital pharmacy procurement even without changing the approved antibody formulation.

6. Analytical and quality-control services

Demand should grow for assays that measure:

• Polysorbate concentration and degradation
• Protein aggregation
• Subvisible and visible particles
• Oxidation and deamidation
• Charge heterogeneity
• Extractables and leachables
• Container adsorption
• In-use stability after dilution
• Endotoxin and particulate burden

Analytical providers with validated methods accepted in biologics comparability packages have a stronger commercial position than general testing laboratories.

How strong is the KISUNLA formulation opportunity?

The excipient opportunity is moderate for commodity materials and high for differentiated biologics-grade systems.

Opportunity	Technical difficulty	IP potential	Commercial attractiveness
Histidine and sodium chloride supply	Low	Low	Low to moderate
Standard polysorbate 80 supply	Moderate	Low	Moderate
Low-peroxide polysorbate 80	Moderate	Moderate	High
Alternative surfactant	High	High	High
High-concentration donanemab	Very high	High	High
Subcutaneous formulation	Very high	High	Very high
Container-closure optimization	Moderate	Moderate	Moderate to high
Ready-to-use infusion systems	Moderate	Moderate	Moderate
Analytical testing	Moderate	Low to moderate	High

The strongest defensible strategy combines excipient quality, formulation performance, and delivery-system data. A supplier that sells only a standard excipient is vulnerable to price competition. A supplier that supplies the excipient, analytical package, stability data, and regulatory-change support has a stronger position.

What litigation and settlement issues affect KISUNLA?

No specific KISUNLA Paragraph IV litigation framework applies because KISUNLA is a biologic rather than a small-molecule Orange Book product. The relevant future disputes could involve:

• BPCIA patent-listing and patent-exchange procedures
• Composition-of-matter patents
• Antibody sequence or epitope claims
• Manufacturing-process patents
• Formulation patents
• Use patents covering Alzheimer’s disease treatment
• Device and administration patents
• Biosimilar approval and launch timing

Settlement agreements could establish a negotiated biosimilar entry date, licensing terms, manufacturing restrictions, or royalty obligations. The commercial value of a settlement depends on the remaining patent term, the strength of the challenged claims, the size of the Alzheimer’s market, and the cost of biosimilar development.

What is the FDA status of KISUNLA?

The FDA approved KISUNLA on July 2, 2024, for adults with early symptomatic Alzheimer’s disease and confirmed amyloid pathology.[3] The product carries warnings relating to amyloid-related imaging abnormalities, including edema and effusions, and intracerebral hemorrhages. These safety requirements affect demand for infusion services, MRI monitoring, patient selection, and payer coverage.

The safety-monitoring burden creates a secondary commercial market for MRI scheduling, infusion-center capacity, pharmacy preparation, and clinical decision-support systems. It also reduces the relevance of excipient cost as a standalone procurement factor. Product selection will depend on efficacy, dosing interval, safety profile, administration logistics, and total treatment cost.

Key Takeaways

• KISUNLA contains donanemab-azbt in a liquid formulation using histidine, histidine hydrochloride monohydrate, sodium chloride, polysorbate 80, and water for injection.
• Polysorbate 80 is the most commercially important excipient because oxidation and hydrolysis can affect antibody stability and particles.
• The strongest supplier opportunity is a biologics-grade excipient package with impurity control, stability data, and regulatory change support.
• High-concentration, subcutaneous, and ready-to-use presentations offer greater value than standard excipient supply but require substantial development and regulatory work.
• KISUNLA is governed by the biologics and Purple Book framework, not the Orange Book Paragraph IV pathway.
• FDA approval occurred on July 2, 2024. Reference-product exclusivity generally extends for 12 years from first licensure, subject to statutory rules and potential pediatric extension.
• Future biosimilar competition will depend on regulatory exclusivity, patent litigation, manufacturing barriers, market size, and Eli Lilly’s settlement strategy.

FAQs

Can polysorbate 80 be replaced in a KISUNLA biosimilar?

Potentially, but replacement would require evidence that the alternative surfactant does not create clinically meaningful differences in stability, purity, potency, particles, or immunogenicity.

Is KISUNLA a small-molecule drug or a biologic?

KISUNLA is a biologic monoclonal antibody. Its active ingredient is donanemab-azbt.

Could a KISUNLA formulation patent cover standard histidine buffer?

A broad claim limited to standard histidine buffer would face validity and prior-art challenges. Stronger protection would usually require defined composition parameters linked to a demonstrated technical effect.

What is the most valuable future KISUNLA presentation?

A subcutaneous or higher-concentration presentation could have the greatest commercial value because it may reduce infusion-center dependence and administration time. It also carries the greatest technical and regulatory risk.

Do excipients create a biosimilar barrier for donanemab?

Excipients can create formulation and manufacturing barriers, but they do not independently prevent biosimilar development. The central biosimilar requirement is analytical and clinical comparability to the reference product.

References

1. U.S. Food and Drug Administration. (2024). KISUNLA (donanemab-azbt) prescribing information.
2. U.S. Food and Drug Administration. (2024). Purple Book: Database of licensed biological products.
3. U.S. Food and Drug Administration. (2024, July 2). FDA approves treatment for adults with Alzheimer’s disease.
4. Biologics Price Competition and Innovation Act of 2009, 42 U.S.C. § 262.