United States Patent 12,208,086: Bendamustine Liquid-Composition Claims, Scope, and Patent Landscape

U.S. Patent No. 12,208,086 covers a method of treating chronic lymphocytic leukemia (CLL) or indolent B-cell non-Hodgkin's lymphoma (NHL) using a specific bendamustine liquid formulation. The independent claim requires five material elements: bendamustine at about 25 mg/mL, a polyethylene glycol/ethanol solvent system, monothioglycerol, optional sodium hydroxide, and a defined two-year refrigerated impurity limit.

The patent is narrower than a broad formulation patent because infringement requires both use in specified hematologic cancers and administration of a composition meeting the formulation and stability limitations. The claim does not cover every bendamustine formulation, every bendamustine indication, or every concentration.

What does U.S. Patent 12,208,086 claim?

Claim 1 is a product-by-process-style method-of-treatment claim with composition limitations. The claimed treatment requires:

Claim element	Required limitation
Disease	CLL or indolent B-cell NHL
Active ingredient	Bendamustine or pharmaceutically acceptable salt
Concentration	About 25 mg/mL
Solvent	Polyethylene glycol and ethanol
Antioxidant or stabilizer	Monothioglycerol
pH adjuster	Sodium hydroxide may be present
Stability	Total impurities not more than 5% w/w after 24 months at about 2°C to 8°C
Solvent ratio	Ethanol about 2%-25% w/w; PEG about 75%-98% w/w
Measurement	HPLC

The claim is cumulative. A potentially infringing product must satisfy all limitations of claim 1 and must be administered to a patient with one of the two specified diseases.

Claims 2 through 7 narrow the scope:

Claim 2 requires bendamustine hydrochloride.
Claim 3 requires PEG-400.
Claim 4 narrows ethanol to about 2%-5% and PEG to about 90%-98%.
Claim 5 requires a pH of 2.7 to 3.7.
Claim 6 limits the ethyl ester impurity to not more than 0.5% w/w after refrigerated storage for 24 months.
Claim 7 specifies ethanol at 39.45 mg/mL.

How broad is the independent claim?

Claim 1 has meaningful breadth in three areas.

First, it covers bendamustine generally and does not require bendamustine hydrochloride. The claim therefore reaches pharmaceutically acceptable salts, although claim 2 expressly identifies the hydrochloride salt as a narrower embodiment.

Second, it permits a relatively broad solvent range. Ethanol may constitute approximately 2%-25% of the PEG/ethanol solvent mixture, while PEG may constitute approximately 75%-98%. The claim does not require PEG-400, although claim 3 narrows the formulation to that grade.

Third, the claim does not require sodium hydroxide. The word "optionally" means that a formulation can fall within claim 1 without sodium hydroxide, provided the remaining limitations are met.

The principal limiting elements are the disease indication, the 25 mg/mL concentration, the presence of monothioglycerol, and the two-year refrigerated impurity result. These limitations materially reduce the risk that the patent covers unrelated bendamustine presentations.

What formulations are protected by U.S. Patent 12,208,086?

The commercial formulation most closely aligned with the claims is a concentrated bendamustine hydrochloride injection containing PEG-400, ethanol, monothioglycerol, and a pH-adjusting agent. The formulation architecture is designed to address bendamustine degradation in an aqueous injectable environment.

Formulation scope by claim

Formulation characteristic	Claim 1	Narrower dependent claims
Bendamustine concentration of about 25 mg/mL	Yes	Claims 2-7
Bendamustine hydrochloride	Permitted	Claim 2
PEG/ethanol solvent	Required	Claims 3, 4, and 7 narrow the system
PEG-400	Permitted but not required	Claim 3
Ethanol 2%-25% of solvent mixture	Required	Claim 4 narrows to 2%-5%
PEG 75%-98% of solvent mixture	Required	Claim 4 narrows to 90%-98%
Monothioglycerol	Required	Claims 2-7
Sodium hydroxide	Optional	Claims 2-7
pH 2.7-3.7	Not required	Claim 5
Total impurities ≤5% after 24 months refrigerated	Required	Claims 2-7
Ethyl ester impurity ≤0.5%	Not required	Claim 6
Ethanol 39.45 mg/mL	Not required	Claim 7

A formulation containing water as an excipient is not necessarily outside the claim. Claim 1 defines the required solvent mixture as PEG and ethanol but does not expressly exclude water or other excipients. Infringement would depend on the full claim construction, the composition's actual contents, and whether the water changes the relevant solvent-mixture calculation.

How do claims 4 and 7 interact?

Claims 4 and 7 create separate fallback positions.

Claim 4 covers a narrower solvent ratio: ethanol at about 2%-5% and PEG at about 90%-98% of the PEG/ethanol solvent mixture. It is directed to a low-ethanol formulation range.

Claim 7 specifies ethanol at 39.45 mg/mL. Unlike claim 4, it does not expressly repeat the 2%-5% solvent-mixture ratio. It remains dependent on claim 1, so the parent limitations continue to apply. A formulation could potentially satisfy claim 7 while falling outside claim 4 if its ethanol concentration corresponds to a solvent-mixture percentage above 5%, subject to the meaning of "about" and the calculation method used.

The numerical relationship between mg/mL and weight percentage will be important. A litigation analysis would need the formulation density, the total solvent volume, and the patent's specification-based measurement convention.

What is the significance of the impurity limitations?

The stability limitations are central to the patent's enforceability and design-around analysis.

Claim 1 requires total impurities of no more than 5% w/w after storage for 24 months at approximately 2°C to 8°C. Claim 6 separately limits the ethyl ester impurity to no more than 0.5% w/w under the same storage conditions.

These are performance limitations, not merely compositional limitations. A formulation may contain the same excipients and concentration but avoid literal infringement if it cannot satisfy the specified impurity thresholds. Conversely, a manufacturer cannot assess risk solely by comparing ingredient lists. Stability data and validated HPLC methods may be required.

Key technical questions include:

Whether "total impurities" includes identified and unidentified degradation products.
Whether the 24-month test begins at manufacture or another defined time point.
Whether the measurement must use the HPLC method disclosed in the patent specification.
Whether the ethyl ester impurity is measured against total composition weight or another analytical basis.
Whether the phrase "stored at a temperature from about 2°C to about 8°C" requires continuous refrigerated storage.
Whether accelerated or intermediate stability data can establish infringement.

These limitations can provide a substantial design-around opportunity. A competing formulation using a different stabilizer, a different solvent, a different concentration, or a shorter labeled refrigerated shelf life may avoid one or more claim elements.

What method-of-use protection does the patent provide?

The patent is limited to treatment of:

Chronic lymphocytic leukemia; and
Indolent B-cell non-Hodgkin's lymphoma.

It does not expressly cover all NHL, aggressive B-cell NHL, multiple myeloma, solid tumors, or other uses of bendamustine. It also does not claim a specific dosing schedule, infusion duration, cycle length, pretreatment protocol, or combination with an anti-CD20 antibody.

The method-of-use limitation creates a potential distinction between product supply and treatment conduct. A manufacturer may face formulation-patent exposure even where its label includes several indications, but enforcement of the method claim would still depend on the accused use and the relevant prescribing, labeling, distribution, or induced-infringement evidence.

A generic applicant could consider a section viii statement or other labeling strategy for noncovered indications, but that approach would not necessarily eliminate exposure if the marketed formulation itself is alleged to meet the claim and the product is used for the patented indications.

When does U.S. Patent 12,208,086 lose exclusivity?

The patent's expiration date cannot be determined from the claims alone. The term requires the patent's earliest effective nonprovisional filing date, any applicable priority claims, patent-term adjustment, patent-term extension, terminal disclaimers, and the prosecution history.

For a recently issued U.S. patent, the relevant commercial question is not the issue date but the expiration of the underlying patent term. A continuation patent may expire on the same date as an earlier parent patent if subject to a terminal disclaimer. A patent-term adjustment can move the expiration date later, while a terminal disclaimer can prevent a later expiration.

The patent's remaining term should therefore be assessed from the following record:

Term issue	Commercial significance
Earliest effective U.S. nonprovisional filing date	Establishes the base 20-year term
Priority chain	Determines whether earlier applications control term
Patent-term adjustment	May extend expiration for USPTO delay
Patent-term extension	May extend term for qualifying regulatory delay
Terminal disclaimer	May align expiration with another patent
Maintenance fees	Affects continued enforceability
Post-grant proceedings	May cancel or amend claims

No expiration date should be treated as authoritative without that record.

What is the Orange Book status of the patent?

A patent number alone does not establish Orange Book listing status. The FDA Orange Book identifies patents submitted by the NDA holder for an approved drug and indicates whether a listed patent covers the drug substance, drug product, or method of use.

For bendamustine products, the relevant regulatory comparison is between the patent and the specific NDA product, including:

Active ingredient and salt;
Concentration;
Dosage form;
Excipients;
Approved indications;
Listed patent category;
Pediatric exclusivity;
Any patent-use code.

A method-of-treatment patent may be listed with a method-of-use code if it is submitted for the relevant approved product. Listing does not itself establish validity or infringement. It does affect the timing and legal consequences of an abbreviated new drug application (ANDA) filing.

The patent should be checked against the FDA's current Approved Drug Products with Therapeutic Equivalence Evaluations database and the applicable NDA patent listing. [1]

What Paragraph IV challenges could target this patent?

A generic applicant could challenge the patent through a Paragraph IV certification if the patent is listed against the relevant reference product. The principal invalidity and noninfringement theories would likely involve:

Anticipation

The challenger would need a single prior-art reference disclosing every limitation, including:

The specified bendamustine concentration;
PEG and ethanol in the claimed ranges;
Monothioglycerol;
Refrigerated 24-month stability;
The total-impurity threshold; and
Treatment of CLL or indolent B-cell NHL.

A reference disclosing a similar bendamustine formulation without the stability data may not anticipate the claim unless the stability property is inherent and necessarily present.

Obviousness

The likely obviousness attack would combine known bendamustine liquid formulations, PEG/ethanol solvent systems, antioxidants, and routine stability optimization. The patent owner would respond that the impurity profile and long-term refrigerated stability were not predictable from the prior art.

The 25 mg/mL concentration and excipient combination may be vulnerable if comparable injectable formulations were already known. The quantitative impurity limitations may provide the stronger patentability position if the specification demonstrates an unexpected stability advantage.

Written description and enablement

The challenger could test whether the specification supports the full ethanol and PEG ranges, all pharmaceutically acceptable bendamustine salts, optional sodium hydroxide, and the claimed 24-month impurity result across the full scope.

Indefiniteness

The terms "about 25 mg/mL," "about 2%-25%," "about 75%-98%," and "about 39.45 mg/mL" may raise boundary questions. The patent's examples and analytical definitions will determine whether a skilled person can apply those ranges consistently.

How strong is the patent estate?

The individual claim set is commercially relevant but structurally narrow. Its strength depends on the relationship between the formulation and the marketed bendamustine product.

Strength factor	Assessment
Product concentration	Strong if the commercial product is approximately 25 mg/mL
PEG/ethanol system	Strong against formulations using the same solvent architecture
Monothioglycerol	Potentially strong if competitors need the same stabilizer
Refrigerated stability limitation	Provides a technical barrier but creates proof burdens
CLL and indolent NHL limitation	Narrows enforcement to specified uses
Broad bendamustine salt language	Expands claim 1 beyond bendamustine hydrochloride
Dependent pH and impurity claims	Provides narrower fallback claims
Exact ethanol concentration in claim 7	Useful if aligned with the commercial formulation

The estate is strongest when the marketed product matches the claimed formulation and the patent specification contains robust examples supporting the impurity limits. It is weaker against a formulation that uses a different stabilizer, changes the PEG/ethanol ratio, changes concentration, or demonstrates a different impurity profile.

What generic launch scenarios exist?

A generic launch would generally follow one of four paths:

Paragraph III filing: The applicant accepts that the patent remains in force and delays approval or launch until expiration.
Paragraph IV challenge: The applicant alleges invalidity, unenforceability, or noninfringement and may trigger patent litigation.
Section viii carve-out: The applicant removes a patented method of use where permitted, although this is more difficult when the patent's principal commercial value lies in the formulation used for the approved indication.
Design-around formulation: The applicant develops a different solvent, stabilizer, concentration, or impurity profile.

A formulation design-around may be more practical than a method-of-use carve-out because the patent claims the administration of a composition rather than only a dosing regimen.

What manufacturing and geographic barriers apply?

The claims are U.S.-specific. They do not directly control manufacturing, sale, or use outside the United States. Separate national patent rights must be assessed in each jurisdiction, including Europe, Canada, Japan, and other markets where bendamustine products are commercialized.

Manufacturing risk is concentrated in:

Selection of the solvent system;
Control of bendamustine degradation;
Monothioglycerol compatibility;
pH adjustment;
Refrigerated shelf-life validation;
HPLC impurity testing;
Batch-release specifications.

A manufacturer can avoid literal composition limitations but still face process or formulation patents in the same family or related families. A complete freedom-to-operate review should therefore distinguish the issued claims in U.S. Patent 12,208,086 from pending continuation claims and earlier or later family patents.

Does biosimilar risk apply to bendamustine?

No. Bendamustine is a small-molecule drug, not a biologic. The relevant competitive pathway is an ANDA for a generic drug, not a biosimilar application under the Public Health Service Act.

The commercial analysis should focus on ANDA patent certifications, therapeutic equivalence, formulation sameness, labeling, drug-shortage conditions, manufacturing capacity, and potential 180-day exclusivity for a first Paragraph IV filer.

Key Takeaways

U.S. Patent 12,208,086 claims treatment of CLL or indolent B-cell NHL using a 25 mg/mL bendamustine liquid composition.
The formulation must contain PEG, ethanol, and monothioglycerol, with optional sodium hydroxide.
Claim 1 requires total impurities of no more than 5% after 24 months at approximately 2°C to 8°C.
Claim 6 adds a stricter ethyl ester impurity limit of 0.5%.
Claims 2 through 5 and 7 provide narrower positions covering bendamustine hydrochloride, PEG-400, low ethanol, pH 2.7-3.7, and ethanol at 39.45 mg/mL.
The patent does not cover every bendamustine product or every bendamustine indication.
Generic risk depends heavily on whether the proposed product uses the same PEG/ethanol/monothioglycerol architecture and meets the stability limitations.
Bendamustine has generic, not biosimilar, competition.
The patent expiration date and Orange Book status require review of the patent record, priority chain, prosecution history, and FDA listing data.

FAQs

Does the patent cover bendamustine tablets?

No. The provided claims are directed to administration of a liquid bendamustine composition. They do not expressly cover oral tablets or capsules.

Can a competitor avoid the patent by using bendamustine at 10 mg/mL?

Potentially. Claim 1 requires about 25 mg/mL. A materially different concentration may avoid literal infringement, although the complete patent family and doctrine-of-equivalents exposure would require separate analysis.

Is monothioglycerol required?

Yes. Claim 1 requires monothioglycerol. A formulation without monothioglycerol may have a noninfringement position under the literal claim, subject to other claims in the patent family.

Does a nonrefrigerated product avoid the claims?

Potentially, but not automatically. The claim defines an impurity result after storage at approximately 2°C to 8°C. A product's labeled storage condition is relevant, but infringement analysis would depend on whether the composition satisfies the claimed test condition.

Is a patent lawsuit required before a generic can launch?

No. A generic applicant may file a Paragraph IV certification and obtain approval after resolving litigation, settling with the patent owner, prevailing in court, or reaching the applicable statutory date. A launch before patent expiry can still create infringement exposure.

References

U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations. https://www.accessdata.fda.gov/scripts/cder/ob/
U.S. Patent and Trademark Office. (2025). United States Patent No. 12,208,086. U.S. Department of Commerce.
U.S. Food and Drug Administration. (n.d.). Bendeka (bendamustine hydrochloride) injection prescribing information. FDA.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Azurity	VIVIMUSTA	bendamustine hydrochloride	SOLUTION;INTRAVENOUS	212209-001	Dec 7, 2022		RX	Yes	Yes	⤷ Start Trial	⤷ Start Trial	Y				⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>TE	>Type	>RLD	>RS	>Patent No.	>Patent Expiration	>Product	>Substance	>Delist Req.	>Patented / Exclusive Use	>Submissiondate

Details for Patent: 12,208,086

Which drugs does patent 12,208,086 protect, and when does it expire?

Summary for Patent: 12,208,086