List of Excipients in Branded Drug HALAVEN

Company	Tradename	Ingredient	NDC	Excipient	Potential Generic Entry
BSP Pharmaceuticals SpA	HALAVEN	eribulin mesylate	43624-002	ALCOHOL
BSP Pharmaceuticals SpA	HALAVEN	eribulin mesylate	43624-002	WATER
Eisai Inc	HALAVEN	eribulin mesylate	62856-389	ALCOHOL
Eisai Inc	HALAVEN	eribulin mesylate	62856-389	HYDROCHLORIC ACID
Eisai Inc	HALAVEN	eribulin mesylate	62856-389	SODIUM HYDROXIDE

Halaven Excipient Strategy and Commercial Opportunities for Eribulin Mesylate

Last updated: August 8, 2026

Halaven is a preservative-free intravenous eribulin mesylate injection with a simple excipient profile: ethanol and water for injection. The formulation has low excipient complexity, which supports generic development but leaves limited room for broad composition-of-matter differentiation. The strongest commercial opportunities are alcohol-free presentations, ready-to-administer oncology products, extended-stability premixes, and packaging or administration systems that reduce preparation risk.

The primary regulatory route for an equivalent product is an ANDA under section 505(j) of the Federal Food, Drug, and Cosmetic Act. A materially different formulation, route, dosage form, or administration profile would more likely require a 505(b)(2) application in the United States. The foundational eribulin compound patent has expired, while formulation and method-of-use barriers must be assessed against current FDA Orange Book records and jurisdiction-specific patent registers. [1-3]

What excipients are used in Halaven?

Halaven contains eribulin mesylate in an aqueous ethanol vehicle.

Product attribute	Halaven profile
Active ingredient	Eribulin mesylate
Strength	1 mg per 2 mL vial
Dosage form	Sterile intravenous solution
Preservative	None identified in the US prescribing information
Excipients	Ethanol and water for injection
Administration	Intravenous injection or dilution in 0.9% sodium chloride
Manufacturer	Eisai Inc. in the United States
Primary use	Metastatic breast cancer and unresectable or metastatic liposarcoma after prior anthracycline exposure
Regulatory pathway for generic	ANDA, subject to applicable patent certifications

The US prescribing information describes Halaven as a sterile, preservative-free, clear, colorless solution. Each 2 mL vial contains 1 mg of eribulin mesylate. The product is administered intravenously over approximately two to five minutes, and the dose may be diluted in 100 mL of 0.9% sodium chloride for injection. [1]

The formulation’s simplicity reduces manufacturing complexity and the risk of excipient-related bioequivalence disputes. It also limits opportunities to obtain broad protection through routine excipient substitution.

Why does Halaven use ethanol as an excipient?

Ethanol is used as a cosolvent to support the solubility and physical stability of eribulin mesylate in a small-volume injectable product. The vehicle permits presentation as a ready sterile solution rather than a lyophilized powder requiring reconstitution.

The commercial benefits are substantial:

• No reconstitution step is required.
• The vial has a low fill volume.
• The formulation avoids surfactants such as polysorbates or polyoxyethylated castor oil.
• The product can be diluted into normal saline before infusion.
• Manufacturing does not require a lyophilization cycle.

The disadvantages are also material. Ethanol creates handling, labeling, compatibility, and patient-exposure considerations. These issues are most relevant for pediatric use, patients with alcohol sensitivity, institutions applying alcohol-free policies, and jurisdictions with strict excipient disclosure requirements.

The formulation therefore creates a credible development target for an alcohol-free eribulin product, but a substitute vehicle must preserve solubility, chemical stability, particulate control, container compatibility, and dose-concentration performance.

What formulations are protected by Halaven-related patents?

The core eribulin patent estate was built around synthetic halichondrin B analogs rather than a complex excipient platform. US Patent No. 6,214,377 covers halichondrin B analog compounds that include eribulin-related chemical matter. The patent has reached the end of its ordinary commercial life, removing the principal composition-of-matter barrier in the United States. [2]

A formulation review should separate four categories of rights:

Patent category	Relevance to an eribulin product
Composition of matter	Historically protected eribulin and related halichondrin analogs
Formulation	Could cover solvents, buffers, pH ranges, concentrations, containers, or stability systems
Method of use	Could cover treatment of breast cancer, liposarcoma, or dosing schedules
Manufacturing process	Could cover synthesis, purification, crystallization, salt formation, or sterile manufacture

The practical risk for a generic injection is usually lower for excipient substitution than for a new therapeutic indication. A formulation that uses the same active ingredient, strength, route, and dosage form may qualify for ANDA approval if it meets pharmaceutical equivalence and bioequivalence requirements and does not infringe an unexpired patent.

A 505(b)(2) product has greater freedom to claim a distinct formulation or administration benefit, but it also faces a higher evidentiary and regulatory burden. FDA may require bridging studies, additional stability data, extractables and leachables work, local tolerance data, or clinical support for a changed exposure profile.

What is the Orange Book status of Halaven?

FDA Orange Book analysis should focus on three questions:

1. Which patents remain listed against the reference listed drug?
2. What expiration dates and pediatric extensions apply?
3. Are any listed method-of-use patents relevant to the proposed label?

Halaven’s original listed patent protection was directed primarily to eribulin-related chemical matter. The expiration of the foundational patent substantially reduces the risk for a conventional eribulin mesylate injection. Current Orange Book records remain the controlling source for any active listing, pediatric extension, or use code. [3]

A generic applicant must still review:

• FDA Orange Book patent listings.
• The reference product’s labeling and dosage form.
• Paragraph IV certifications.
• Any patent litigation filed after certification.
• State and federal injunctions affecting launch.
• Patent rights in Europe, Japan, Canada, and other target markets.

The existence of an expired composition patent does not automatically eliminate formulation or process risk. A separate formulation patent can affect an ANDA if it is listed and unexpired, while an unlisted patent may still create litigation exposure even if it does not block FDA approval.

When does Halaven lose exclusivity?

Halaven received US approval in 2010. New chemical entity exclusivity would have expired five years after approval, subject to the timing of any patent certifications and regulatory exclusivity periods. The key commercial barrier was patent protection rather than long-term regulatory exclusivity. [1,3]

Exclusivity element	Halaven impact
US approval	2010
NCE exclusivity	Expired
Orphan-drug exclusivity	Not the central exclusivity mechanism for the breast cancer indication
Core compound patent	Expired
Generic pathway	ANDA availability is the principal route
Biosimilar pathway	Not applicable
Current competitive risk	Generic injection and differentiated 505(b)(2) products

Halaven is a small-molecule drug. Biosimilar competition is therefore irrelevant. Competition comes from generic eribulin injections, therapeutic alternatives, and products that improve administration economics.

Which companies are challenging Halaven with generics?

Generic competition is likely to come from injectable oncology manufacturers with sterile-fill capabilities, including global generic firms, contract manufacturing organizations, and established hospital-product suppliers. The relevant FDA pathway is an ANDA for eribulin mesylate injection.

The commercial screening process should examine:

• FDA approvals for eribulin mesylate injection.
• Tentative approvals.
• Drug shortages and supply interruptions.
• ANDA holders and authorized distributors.
• Paragraph IV litigation records.
• Product availability by vial size.
• Wholesale acquisition cost and institutional contract pricing.

An applicant offering the same 1 mg/2 mL presentation will compete primarily on price, supply reliability, contract access, and quality history. A differentiated excipient strategy matters most when it removes a clinically or operationally meaningful limitation.

What are the strongest excipient opportunities for Halaven?

Alcohol-free eribulin injection

An alcohol-free vehicle is the clearest formulation opportunity. Potential solvent systems may include aqueous cosolvent combinations, pH-controlled systems, complexing agents, or other solubilization technologies. The product must maintain a comparable concentration and injectable profile without introducing a new safety or administration burden.

A successful alcohol-free formulation could be positioned for:

• Patients with alcohol intolerance or contraindications.
• Pediatric or adolescent use where clinically relevant.
• Hospitals with alcohol-restricted formularies.
• Markets requiring reduced excipient exposure.
• Premixed or ready-to-use oncology distribution.

The principal patent risk is that a specific cosolvent, buffer range, complexing agent, or concentration may be claimed by a formulation patent. Broad claims are more difficult to obtain for conventional excipients, but narrow claims based on stability, impurity control, or container interaction can be commercially useful.

Ready-to-administer bags or syringes

Halaven is supplied in a vial and may be diluted before infusion. A ready-to-administer presentation could reduce pharmacy preparation time and exposure to cytotoxic handling procedures.

Possible formats include:

• A fixed-dose infusion bag.
• A pharmacy-ready syringe.
• A vial-plus-diluent kit.
• A low-volume premix.
• A closed-system transfer-compatible container.

The main development barriers are stability after dilution, microbial control, adsorption, extractables and leachables, oxygen sensitivity, and compatibility with infusion devices. A premix may require a 505(b)(2) strategy if it differs materially from the approved vial presentation.

Extended in-use stability

A formulation with longer post-puncture or post-dilution stability could generate value even without changing the active ingredient. Hospitals could reduce waste and improve scheduling flexibility.

Protection may be available through claims covering:

• A defined concentration range.
• A specified storage temperature.
• A particular diluent.
• A maximum impurity level.
• Container closure materials.
• A stability period after dilution.

Stability claims require reproducible analytical data and a clear technical relationship between the formulation and the claimed shelf life.

Lower-volume administration

Halaven is already supplied in a 2 mL vial, so volume reduction alone has limited commercial value. The stronger opportunity is a product that maintains dose accuracy while reducing dilution, preparation, or infusion time.

A higher concentration could improve logistics but creates risks involving local tolerability, dosing errors, precipitation, and line compatibility. Any concentration change would require careful regulatory classification.

How does Halaven compare with competing oncology injections?

Product	Key excipient issue	Commercial implication
Halaven, eribulin mesylate	Ethanol and water for injection	Simple solution; alcohol-related differentiation opportunity
Paclitaxel	Polyoxyethylated castor oil and ethanol	Hypersensitivity management and infusion-premedication burden
Docetaxel	Polysorbate 80 and ethanol in certain presentations	Formulation and hypersensitivity concerns
Ixabepilone	Complex solvent and diluent system	More reconstitution and handling complexity
Vinorelbine	Aqueous injectable solution	Competes on price and established hospital use

Halaven’s excipient profile is operationally simpler than several taxane formulations. That weakens the case for a broad excipient replacement unless the new product delivers a specific benefit, such as elimination of ethanol, longer stability, or reduced preparation requirements.

What generic launch risks exist for Halaven?

Paragraph IV challenges

An ANDA applicant may file a Paragraph IV certification against any unexpired listed patent. The applicant can trigger litigation by providing notice to the patent holder. A lawsuit may impose a 30-month stay on FDA approval, subject to statutory exceptions and court action. [4]

For Halaven, the most important Paragraph IV questions are:

• Whether any active patent remains listed.
• Whether the patent claims the proposed formulation or use.
• Whether the proposed label omits the patented indication.
• Whether a section viii statement can remove the patented use.
• Whether the applicant can launch at risk after patent expiry or litigation resolution.

Manufacturing and sterile-fill barriers

The principal manufacturing barrier is not excipient sourcing. It is sterile injectable production. A competitive supplier needs:

• Validated aseptic processing.
• Low bioburden and endotoxin control.
• Container closure integrity.
• Reliable eribulin mesylate sourcing.
• Control of visible and subvisible particles.
• Scalable fill-finish capacity.
• Adequate oncology distribution channels.

A supplier with an established sterile injectable network can enter more efficiently than a company that must build a new facility.

Supply and procurement risk

Hospital purchasing organizations often evaluate generic oncology products on supply continuity, shortage history, vial economics, and contract terms. A differentiated formulation has limited value if the product cannot maintain reliable availability.

The strongest commercial model may combine a standard ANDA product for volume with a differentiated formulation for higher-margin institutional accounts.

How strong is the patent estate for an excipient-based Halaven product?

The patent estate is likely strongest for a narrow, data-supported formulation claim rather than for generic use of a common excipient. Potentially valuable claim themes include:

1. An alcohol-free eribulin solution with defined pH and concentration.
2. A formulation with reduced degradation products during storage.
3. A premixed eribulin infusion product with extended stability.
4. A specific container closure that limits adsorption or extractables.
5. A formulation compatible with a closed-system transfer device.
6. A composition that reduces preparation errors or dilution requirements.

Patent strength depends on unexpected technical results. A claim that simply replaces ethanol with another standard cosolvent may face obviousness challenges. A formulation that achieves long-term stability, low particulate levels, and clinically useful concentration without ethanol has a stronger inventive-step position.

What licensing deals affect Halaven excipient opportunities?

Public product information identifies Eisai as the original sponsor and manufacturer of Halaven in the United States. The US label does not identify an excipient technology license, proprietary delivery platform, or co-development partner for the marketed formulation. [1]

A licensing transaction could be justified for:

• A validated alcohol-free solubilization platform.
• A ready-to-use oncology premix technology.
• A proprietary container or closed-system transfer format.
• A sterile-fill partnership in regions lacking local capacity.
• A formulation patent with enforceable geographic coverage.

The preferred deal structure would usually separate the low-margin standard generic from the premium formulation. A partner could receive territory-specific rights, milestone payments tied to regulatory approval, and royalties based on net sales of the differentiated product.

What is the commercial outlook for Halaven excipient innovation?

Halaven’s revenue exposure is concentrated in oncology institutions, where pharmacy labor, preparation safety, and supply reliability influence purchasing. Public sources do not provide a reliable revenue allocation attributable specifically to the ethanol-containing formulation. The opportunity should therefore be assessed through addressable institutional volume, generic price erosion, and the premium that hospitals would pay for reduced preparation complexity.

Opportunity	Regulatory burden	Differentiation potential	Commercial attractiveness
Conventional generic vial	Low to moderate	Low	High for volume
Alcohol-free vial	Moderate	Medium to high	Selective
Premixed infusion bag	Moderate to high	High	High if stability is proven
Prefilled syringe	High	Medium	Selective
Extended-stability diluted product	Moderate	Medium	Moderate
New route or dosage form	High	High	Uncertain

The most defensible strategy is a two-track program: file a conventional ANDA for market access, then develop a differentiated formulation through a 505(b)(2) or supplemental strategy if the technical package supports a meaningful clinical or operational advantage.

Key Takeaways

• Halaven is a preservative-free eribulin mesylate injection using ethanol and water for injection.
• Its simple formulation supports generic competition but limits broad excipient patent opportunities.
• The strongest formulation concept is an alcohol-free eribulin injection with equivalent stability and administration performance.
• Ready-to-administer bags, syringes, and extended-stability premixes could create higher-value hospital products.
• Biosimilar competition does not apply because eribulin is a small molecule.
• The principal regulatory route for an equivalent product is an ANDA.
• A materially different formulation may require a 505(b)(2) application.
• Patent review must cover Orange Book listings, formulation claims, method-of-use claims, and manufacturing patents across target jurisdictions.
• Sterile manufacturing capacity and supply reliability are likely to matter more than excipient cost.
• A conventional generic and a premium differentiated formulation can be developed as separate commercial products.

FAQs

Can ethanol be removed from Halaven without changing the active ingredient?

Yes, in principle. The replacement formulation must demonstrate equivalent quality, stability, sterility, particulate control, container compatibility, and appropriate regulatory performance. Removing ethanol does not by itself establish pharmaceutical equivalence.

Would an alcohol-free eribulin product be an ANDA or 505(b)(2) application?

The answer depends on the extent of formulation and labeling differences. A formulation that remains pharmaceutically equivalent may qualify for an ANDA. A product with a materially different vehicle, concentration, presentation, or administration profile may require a 505(b)(2) application.

Are formulation patents more important than the expired eribulin compound patent?

For a new entrant, yes. Once the composition-of-matter patent has expired, unexpired formulation, method-of-use, process, and device patents become the relevant barriers.

Can Halaven be sold as a prefilled syringe?

A prefilled syringe is technically possible but would require assessment of stability, syringe materials, extractables and leachables, dose accuracy, container closure integrity, and compatibility with oncology administration systems.

Is there a biosimilar pathway for eribulin?

No. Eribulin is a chemically synthesized small-molecule drug. Competition proceeds through generic drug pathways rather than the biologic biosimilar framework.

References

1. U.S. Food and Drug Administration. (2024). Halaven (eribulin mesylate) injection: Prescribing information. Eisai Inc.
2. U.S. Patent No. 6,214,377. (2001). Halichondrin B analogs. United States Patent and Trademark Office.
3. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
4. U.S. Food and Drug Administration. (2017). Guidance for industry: 180-day exclusivity when multiple ANDA applicants are eligible for 180-day exclusivity.