List of Excipients in Branded Drug FUSILEV

Company	Tradename	Ingredient	NDC	Excipient	Potential Generic Entry
Acrotech Biopharma Inc	FUSILEV	levoleucovorin	72893-009	HYDROCHLORIC ACID
Acrotech Biopharma Inc	FUSILEV	levoleucovorin	72893-009	MANNITOL
Acrotech Biopharma Inc	FUSILEV	levoleucovorin	72893-009	SODIUM HYDROXIDE

FUSILEV Excipient Strategy and Commercial Opportunities

Last updated: August 25, 2026

FUSILEV is an injectable levoleucovorin calcium product whose commercial value depends more on presentation, supply reliability, concentration, and hospital workflow than on excipient differentiation. The marketed formulation uses a conventional, preservative-free aqueous vehicle with sodium chloride and pH adjustment. That composition creates limited standalone excipient patent value, but it supports opportunities in ready-to-use dosing, stability, pharmacy labor reduction, shortage supply, and differentiated container systems.

What is FUSILEV and what excipients does it contain?

FUSILEV contains levoleucovorin calcium, the pharmacologically active levo-isomer of folinic acid. It is administered intravenously for methotrexate rescue and in combination with fluorouracil for colorectal cancer treatment. The FDA-approved product is supplied as a sterile, preservative-free injectable solution.

The approved labeling identifies the following formulation components:

Component	Function	Commercial relevance
Levoleucovorin calcium	Active pharmaceutical ingredient	Chiral folate rescue and fluorouracil modulation
Sodium chloride	Isotonicity and vehicle support	Commodity excipient; low differentiation
Hydrochloric acid and/or sodium hydroxide	pH adjustment	Critical to chemical stability and injectability
Water for injection	Solvent	Standard parenteral vehicle

The precise excipient composition can vary by strength and manufacturing presentation. The current FDA labeling and product-specific prescribing information should control any development or regulatory assessment.[1]

FUSILEV is not a biologic. Biosimilar substitution rules do not apply. Competitive risk comes from generic levoleucovorin calcium injections, racemic leucovorin products, hospital compounding, and alternative folinic-acid presentations.

What formulation strategy does FUSILEV use?

FUSILEV uses a low-complexity parenteral formulation. Its main formulation attributes are:

• Preservative-free administration
• Aqueous intravenous delivery
• Sodium chloride-based tonicity control
• pH adjustment rather than a complex buffer system
• Single-dose packaging
• Concentration suitable for dilution before infusion

This strategy reduces excipient-related toxicity and simplifies compatibility assessment. It also limits the ability to create broad formulation exclusivity around the core product.

The commercial tradeoff is clear. A simple formulation can reduce manufacturing cost and regulatory burden, but competitors can often reproduce the excipient platform through an abbreviated new drug application if they match the relevant quality and performance requirements.

What excipient functions are technically important?

pH control

Levoleucovorin calcium is sensitive to formulation conditions that affect solubility, degradation, color, and compatibility. Hydrochloric acid and sodium hydroxide are used to establish the target pH range. The pH window must support:

• Chemical stability during shelf life
• Prevention of visible and subvisible particulate formation
• Compatibility with common infusion diluents
• Acceptable intravenous tolerability
• Consistent assay and impurity profiles

A pH-adjusted formulation without a conventional buffer can reduce buffer-related interactions. The tradeoff is that manufacturing control becomes more dependent on raw-material quality, mixing order, temperature, and container closure performance.

Sodium chloride

Sodium chloride provides isotonicity and contributes to a familiar hospital-use profile. It is inexpensive and widely available. It is unlikely to create meaningful formulation patent protection by itself.

The main commercial issue is total sodium exposure in patients receiving repeated or high-dose regimens. Product labeling, dilution volume, and institutional protocols determine the practical significance of sodium content.

Water for injection

Water for injection is the standard parenteral solvent. Its strategic value is operational rather than proprietary. Water quality, bioburden control, endotoxin control, and aseptic processing are central to product quality.

Preservative-free design

The absence of antimicrobial preservatives is important for intravenous oncology use. It reduces concerns relating to preservative toxicity and compatibility, particularly when the product is administered to patients receiving intensive chemotherapy.

The disadvantage is that single-dose containers and strict aseptic manufacturing are required. A multidose presentation would introduce additional preservative, sterility, and regulatory complexity.

What formulations are protected by FUSILEV-related patents?

The core excipient combination is unlikely to provide a strong standalone patent position because it relies on common parenteral ingredients. Potentially protectable subject matter would more likely involve:

1. A defined concentration range of levoleucovorin calcium.
2. A specific pH range linked to improved stability.
3. A low-degradation formulation under refrigerated or room-temperature storage.
4. A container closure system that limits adsorption, oxidation, or particulate formation.
5. A ready-to-use bag or syringe presentation.
6. A defined dilution protocol or admixture stability period.
7. A manufacturing process that controls impurities or stereochemical integrity.
8. A formulation compatible with a particular infusion device.

A patent claim directed only to levoleucovorin, sodium chloride, water, and pH adjustment would face substantial validity and obviousness pressure unless the applicant can show an unexpected stability, compatibility, or safety result.

An excipient strategy can still support intellectual property when the claim is tied to a measurable technical result. Examples include longer room-temperature stability, reduced degradation after dilution, lower particulate burden, or improved delivery through a closed-system transfer device. The evidence must establish that the result derives from the claimed formulation or process rather than routine optimization.

Does FUSILEV have Orange Book formulation or method-of-use protection?

FUSILEV's principal regulatory value comes from its approved active ingredient and indications rather than from a distinctive excipient platform. Orange Book protection, where applicable, would depend on patents submitted for the relevant NDA and accepted by FDA under the applicable listing rules.[2]

Potential listing categories include:

• Drug substance patents
• Drug product or formulation patents
• Method-of-use patents
• Device or delivery patents, if they meet applicable listing requirements

Excipient-only claims generally have limited Orange Book leverage unless they claim the approved drug product or a method of use in a manner that satisfies FDA listing standards. A patent covering a manufacturing process may have commercial importance but may not create the same direct barrier to an ANDA as a listed drug-product or method-of-use patent.

The FDA label does not make the excipient platform appear to be the primary source of market exclusivity. Any current patent conclusion must be based on the live Orange Book patent table and the relevant patent records, not on the formulation description alone.[2]

When does FUSILEV lose exclusivity?

FUSILEV's exclusivity profile is determined by several separate events:

Exclusivity or barrier	Relevance to FUSILEV
New chemical entity exclusivity	Generally not the principal pathway for a levoleucovorin product with an established folate active moiety
Three-year clinical investigation exclusivity	May apply to qualifying supplemental approvals
Orphan-drug exclusivity	Depends on the specific indication and designation
Listed patents	May delay ANDA approval if valid and enforceable
Regulatory exclusivity for the original product	Separate from patent expiry and must be reviewed in FDA records
Injectable manufacturing barriers	Can delay entry even when legal exclusivity has ended

Patent expiry and regulatory exclusivity are not interchangeable. A generic applicant may file before patent expiry and submit Paragraph IV certifications against listed patents. FDA approval timing then depends on patent litigation, statutory stays, exclusivity, and the ANDA's technical status.[3]

What Paragraph IV challenges and generic-entry risks exist?

Paragraph IV risk is most relevant to any remaining listed patent covering:

• Levoleucovorin calcium composition
• The approved injectable formulation
• A specific oncology method of use
• A ready-to-administer presentation
• Stability or packaging features that are legally listed

The excipient platform creates limited defensive value if competitors can develop materially equivalent formulations with different pH adjustment or tonicity approaches. A generic applicant could potentially use:

• Sodium chloride at a different concentration
• A different pH-adjustment profile
• A phosphate-free or alternative buffered system
• A different vial fill volume
• A lyophilized presentation reconstituted before use
• A ready-to-dilute concentrate

The primary generic-entry risks are therefore substitution flexibility and the availability of routine parenteral excipients. The stronger barriers are usually sterile manufacturing, validated stability, particulate control, container closure integrity, and commercial-scale supply.

What manufacturing and intellectual-property barriers matter most?

Sterile manufacturing

The largest practical barrier is aseptic injectable manufacturing. A competitor needs validated sterilization or aseptic processing, endotoxin control, environmental monitoring, container closure integrity, and reproducible filling.

Stability and degradation control

Levoleucovorin products must maintain potency and impurity limits through shipping, storage, dilution, and administration. Stability data can support both regulatory approval and differentiated commercial claims.

Container closure systems

Glass vials are conventional, but elastomer selection, extractables and leachables, oxygen exposure, and stopper compatibility can affect product quality. A polymer vial, prefilled syringe, or infusion bag could offer commercial differentiation if it improves handling or shelf life.

Admixture compatibility

FUSILEV labeling contains important administration restrictions. Levoleucovorin calcium should not be mixed in the same infusion with fluorouracil because precipitation can occur. The products are administered sequentially or according to an established institutional protocol rather than as an unvalidated premixed solution.[1]

That restriction limits one obvious commercial opportunity: a simple premixed FUSILEV/fluorouracil product. A co-packaged system with separate chambers, validated sequential delivery, or a closed-system administration kit may be more feasible than a single-container admixture.

What commercial opportunities exist for excipient-based differentiation?

Ready-to-use presentations

Hospitals value products that reduce pharmacy preparation time and handling. Opportunities include:

• Ready-to-administer diluted bags
• Standardized oncology doses
• Prefilled syringes for controlled dosing
• Unit-dose containers for outpatient infusion centers
• Barcode-enabled packaging

The regulatory and stability burden is higher than for a conventional vial, but the product can compete on total cost of use rather than acquisition price alone.

Extended stability after dilution

A formulation that remains stable for a defined period after dilution can reduce waste and improve scheduling. This opportunity requires data on potency, degradation products, pH, osmolality, visible particles, subvisible particles, and container compatibility.

A robust diluted-product stability package could support:

• Longer pharmacy beyond-use periods
• Reduced batch discard
• More flexible treatment scheduling
• Centralized compounding
• Lower occupational exposure through fewer preparation events

Alternative concentrations

FUSILEV dosing is based on clinical regimen and body-surface-area requirements. A higher-concentration vial could reduce injection volume and preparation steps. A lower-concentration presentation could support pediatric or weight-based dosing.

Concentration changes create formulation and safety issues. High-concentration products may increase local tolerability concerns and require new extractables, particulate, and administration studies. Low-concentration presentations may increase vial count and packaging cost.

Closed-system transfer and administration

A vial designed for closed-system transfer devices can improve pharmacy handling and reduce transfer steps. This is a delivery-system opportunity rather than a conventional excipient opportunity. Commercial value may come from integration with oncology compounding systems and institutional purchasing contracts.

Supply continuity

Levoleucovorin is used in chemotherapy regimens where treatment schedules are time-sensitive. A supplier with reliable active-ingredient sourcing, dual manufacturing sites, and adequate vial inventory can compete even without a novel formulation.

The strongest supply proposition would combine:

• Multiple qualified API sources
• Redundant sterile fill capacity
• Long-dated inventory
• Transparent shortage communication
• Standardized vial strengths
• Contract manufacturing flexibility

How does FUSILEV compare with generic leucovorin and other folate products?

Attribute	FUSILEV	Generic levoleucovorin	Racemic leucovorin
Active form	Levoleucovorin calcium	Levoleucovorin calcium	Mixture of folinate stereoisomers
Formulation differentiation	Limited in the conventional vial	Usually designed to be pharmaceutically equivalent	May use different concentration or presentation
Regulatory pathway	NDA or supplemental NDA	ANDA, where applicable	NDA or ANDA depending on product
Biosimilar risk	None	None	None
Main competitive lever	Brand, supply, workflow, clinical familiarity	Price and supply	Price, availability, established use
Excipient IP potential	Moderate only for advanced presentations	Low for routine excipient combinations	Low unless tied to a specific formulation or use

FUSILEV can retain commercial value if it offers dependable availability, better workflow, or a differentiated administration format. A routine vial with commodity excipients is more exposed to price competition.

Which licensing and partnering opportunities are most attractive?

Licensing opportunities are more likely to arise around delivery and manufacturing than around sodium chloride or pH adjustment. Attractive targets include:

• Ready-to-use oncology infusion platforms
• Long-stability liquid formulations
• Prefilled syringe technologies
• Dual-chamber or sequential-delivery devices
• Closed-system transfer compatibility
• Sterile fill-finish capacity
• Regional distribution rights
• Hospital purchasing and specialty-pharmacy channels

A partner with established oncology distribution can add value if it controls infusion-center access or shortage-response capacity. A technology partner is more valuable when it brings validated stability, container systems, or delivery-device IP that can support a differentiated product claim.

A license based solely on a conventional excipient mixture would likely have weak negotiating leverage. A license tied to reduced waste, reduced preparation time, or extended post-dilution stability has clearer economic value.

What is the FDA regulatory status of FUSILEV?

FUSILEV is an FDA-approved prescription injectable product. Its label covers use in methotrexate rescue and in combination with fluorouracil for colorectal cancer treatment.[1]

Regulatory development for a new FUSILEV presentation would depend on the extent of change:

Proposed change	Likely regulatory issue
Different vial size with same formulation	CMC, stability, container closure, and labeling review
New concentration	Product comparability, safety, dosing, and administration data
Ready-to-use diluted bag	Stability, sterility, container compatibility, and administration data
Prefilled syringe	Device compatibility, extractables, dose accuracy, and human factors
New excipient or buffer	Safety qualification, compatibility, and comparative stability
New indication	Clinical and labeling requirements
Generic equivalent	ANDA pharmaceutical equivalence and bioequivalence framework

A major formulation change may require more than a simple supplement. The regulatory pathway depends on whether the product remains pharmaceutically equivalent to the approved presentation and whether the change affects clinical use.

How strong is the FUSILEV excipient patent estate?

The excipient estate is likely weaker than the manufacturing and delivery estate. A practical assessment is:

IP category	Relative strength
Sodium chloride and water vehicle	Low
Routine pH adjustment	Low to moderate
Narrow pH and stability window	Moderate if supported by unexpected results
Container closure system	Moderate to strong if technically specific
Ready-to-use diluted presentation	Moderate
Closed-system administration	Moderate to strong, depending on claim scope
Sterile manufacturing process	Moderate, but enforcement and listing value vary
Method of use	Potentially stronger than excipient claims if clinically specific

The best opportunity is a layered portfolio: formulation claims, container claims, stability claims, administration claims, and process claims. Each layer should address a different competitor design-around path.

Key Takeaways

• FUSILEV uses a conventional preservative-free aqueous injectable strategy centered on levoleucovorin calcium, sodium chloride, water for injection, and pH adjustment.
• Commodity excipients provide limited standalone patent protection.
• The strongest commercial opportunities are ready-to-use dosing, extended post-dilution stability, closed-system administration, and supply reliability.
• Premixed levoleucovorin/fluorouracil products face compatibility constraints because the drugs should not be mixed in the same infusion without validated controls.
• Generic risk is driven by routine formulation substitutability, sterile manufacturing capacity, stability data, and any active Orange Book-listed patents.
• FUSILEV has no biosimilar risk because it is a small-molecule injectable product.
• A defensible IP strategy should focus on measurable formulation performance, container systems, stability, delivery devices, and manufacturing controls.

FAQs

Can sodium chloride in FUSILEV support a formulation patent?

Usually not by itself. Sodium chloride is a standard parenteral excipient. Patent value would require a defined concentration or combination linked to an unexpected stability, compatibility, or safety result.

Is a preservative-free FUSILEV presentation commercially differentiated?

Yes, but mainly through safety perception, oncology workflow, and product handling. Preservative-free status alone is unlikely to block generic competition.

Could FUSILEV be sold in a prefilled syringe?

Potentially, subject to dose accuracy, syringe compatibility, extractables and leachables, stability, sterility, particulate, and administration requirements. The presentation could reduce pharmacy preparation time.

Can FUSILEV and fluorouracil be sold in one premixed container?

A conventional single-container admixture is constrained by precipitation risk. A validated dual-chamber or sequential-delivery system would be more technically plausible than a simple premixed bag.[1]

What is the most valuable new excipient opportunity for FUSILEV?

An excipient or formulation system that materially extends stability after dilution, reduces waste, and supports a ready-to-administer product has the clearest commercial value. A routine change in tonicity or pH is less likely to justify premium pricing or durable exclusivity.

References

1. U.S. Food and Drug Administration. (n.d.). FUSILEV (levoleucovorin calcium) injection, prescribing information. DailyMed. https://dailymed.nlm.nih.gov/dailymed/
2. U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.accessdata.fda.gov/scripts/cder/ob/
3. U.S. Food and Drug Administration. (2024). Abbreviated new drug application submissions: Refuse-to-receive standards. FDA. https://www.fda.gov/industrial-guidance-compliance-regulatory-information/abbreviated-new-drug-application-anda-submissions-grace-period-policy-questions-and-answers