US Patent 8,946,276: Metronidazole Vaginal Gel Claims, Patent Scope, Expiration, and Competitive Landscape

US Patent 8,946,276 protects methods of treating bacterial vaginosis with a single-dose or short-course intravaginal metronidazole gel containing approximately 1.3 wt% metronidazole, equivalent to about 65 mg per application. The patent is directed primarily to the composition and use of the Nuvessa-type 1.3% vaginal gel, rather than to metronidazole generally.

The principal protection covers an aqueous, mucoadhesive gel that excludes dextrins, cyclodextrins, niacin, niacinamide, and surfactants. Dependent claims add narrow solvent systems, polymer concentrations, viscosity, mucoadhesion, pH, preservatives, stability, and dosing schedules. The commercial significance is concentrated in independent claims 1, 34, and 39, especially claim 39, which recites the core 65 mg, 1.3 wt% intravaginal treatment.

What does US Patent 8,946,276 protect?

The patent protects a treatment method requiring the combined presence of several elements:

Treatment of bacterial vaginosis.
Intravaginal administration.
An aqueous-based gel.
Approximately 1.3 wt% metronidazole.
Approximately 65 mg metronidazole per application.
Water.
Certain formulation or performance characteristics.
Absence of specified excipients.

The independent claims do not broadly cover every metronidazole vaginal product. A product must satisfy the claimed concentration, dose, route, disease indication, and exclusion limitations to create a direct literal infringement risk.

Independent claim	Principal subject matter	Commercial relevance
Claim 1	Intravaginal treatment using approximately 1.3 wt% MTZ and 65 mg per application, with an aqueous gel and specified exclusions	Broadest formulation-and-use claim
Claim 34	Treatment using a 1.3 wt% mucoadhesive gel with at least one listed performance or formulation characteristic	Alternative limitation structure
Claim 39	Treatment using an intravaginal gel containing approximately 65 mg MTZ at approximately 1.3 wt%	Core product-use claim

The claims are method claims. They do not independently claim a composition, a manufacturing process, a container, an applicator, or a method of making the gel.

How do claims 1, 34, and 39 differ?

Claim 1: formulation, dose, and treatment method

Claim 1 requires an aqueous-based gel containing one or more gelling polymers, approximately 1.3 wt% metronidazole, and water. A single application must contain approximately 65 mg metronidazole. The gel must be free of dextrins, cyclodextrins, niacin, niacinamide, and surfactants.

This claim also requires administration to a subject suffering from or diagnosed with BV. A generic manufacturer would not infringe claim 1 merely by selling a 1.3% metronidazole gel if the product were not used intravaginally for BV. In practice, however, an FDA-approved label, prescribing information, promotional materials, or product design can provide evidence of the intended method of use.

Claim 34: alternative performance and formulation limitations

Claim 34 covers a mucoadhesive 1.3% MTZ gel containing approximately 65 mg MTZ per application and having at least one of several listed characteristics. These characteristics include:

Elevated stratum-corneum MTZ levels relative to the MGV comparator;
Reduced receiver-fluid MTZ levels relative to MGV;
Viscosity of approximately 200,000 to 400,000 mPa, likely intended to mean mPa·s;
Mucoadhesion within approximately ±10% of MG33PB;
Water content of approximately 30 wt% to 60 wt%;
Stability of at least six months at 25°C;
Approximately 1 wt% to 3 wt% total mucoadhesive polymers; and
A solvent-system concentration of approximately 40 wt% to 45 wt%.

The “one or more” structure makes claim 34 materially broader than a claim requiring every listed characteristic. A competing product could therefore fall within claim 34 by satisfying only one listed performance limitation, assuming the remaining independent requirements are met.

Claim 39: the central commercial claim

Claim 39 requires an intravaginal BV treatment comprising an aqueous-based gel with:

Approximately 65 mg metronidazole;
Approximately 1.3 wt% MTZ; and
No dextrins, cyclodextrins, niacin, niacinamide, or surfactants.

The claim does not expressly require a gelling polymer, mucoadhesive polymer, particular solvent system, pH, viscosity, preservative, or dosing duration. Those limitations appear in dependent claims 41 through 52.

Claim 39 is therefore the most commercially important claim for a product closely corresponding to the 1.3% single-dose metronidazole vaginal gel. It is also vulnerable to claim-construction disputes over “about,” the scope of “free of,” and the meaning of an aqueous-based gel.

What formulation is described by the dependent claims?

The narrowest and most product-specific formulation appears in claims 30 and 52:

Ingredient	Claimed amount
Metronidazole	Approximately 1.3 wt%
Polycarbophil AA-1	Approximately 2 wt%
Benzyl alcohol	Approximately 2 wt%
Propylene glycol	Approximately 15 wt%
PEG 400	Approximately 25 wt%
Methyl paraben	Approximately 0.02 wt%
Propyl paraben	Approximately 0.08 wt%
Water	Balance

This formulation totals approximately 46.1 wt% before accounting for water and any pH-adjusting materials. The solvent system is built around benzyl alcohol, propylene glycol, and PEG 400. Claims 17 through 20 further narrow the aromatic alcohol and diol/polyether ratios.

The patent therefore protects both a broad formulation concept and a specific solvent-polymer-preservative formulation. A competitor that changes the solvent system, polymer, preservative, or polymer concentration may avoid the narrow claims while still requiring analysis under claims 1, 34, or 39.

What solvent systems are protected?

Claims 7 through 20 define a solvent system intended to dissolve metronidazole at elevated concentration while supporting gel stability and vaginal residence.

The claim hierarchy covers:

One or more solvents with saturated MTZ solubility of at least approximately 20 mg/g;
Preferred solvents with solubility of at least approximately 50 mg/g;
Optional solvents with solubility of approximately 20 mg/g to 25 mg/g;
Lower aromatic alcohols;
Lower aliphatic diols;
Polyoxyalkylenes with molecular weight of approximately 200 to 400;
A diol-to-polyoxyalkylene ratio of approximately 1:1 to 1:2;
Benzyl alcohol, propylene glycol, and PEG 400 combinations; and
A benzyl alcohol content of approximately 3.5 wt% to 5 wt% in certain claims.

Claim 20 is particularly specific. It requires approximately 3.5 wt% to 5 wt% benzyl alcohol, with the balance of the solvent system consisting of propylene glycol and PEG 400 at a propylene glycol-to-PEG 400 ratio of approximately 1:1 to 1:1.67.

A formulation using phenoxyethanol instead of benzyl alcohol may fall within claims 10, 13, or 44, depending on the remaining composition. A formulation using only propylene glycol, without PEG 400 or a qualifying polyoxyalkylene, may avoid several narrower solvent-system claims.

What polymer and rheology limitations apply?

Claims 1, 26, and 51 identify hydroxyethylcellulose, carbomer, and polycarbophil as qualifying gelling or mucoadhesive polymers.

The preferred formulation uses approximately 2 wt% polycarbophil AA-1. The claimed total polymer range is generally approximately 1 wt% to 3 wt%.

Claim 3 requires viscosity of approximately 200,000 mPa to 400,000 mPa at 25°C, measured under a specified controlled-shear-rate protocol using a Bohlin CVO 100 rheometer and the settings identified in Table 11. This testing methodology is important. Viscosity is not a universal value independent of instrument, spindle, shear rate, temperature, and sample preparation.

A competitor may dispute infringement by showing that:

The tested viscosity falls outside the numerical range;
The specified rheometer or test settings were not used;
The product changes viscosity during storage;
The claim’s unit should be interpreted as mPa·s rather than mPa; or
The tested formulation is not representative of the commercial product.

What dosing regimens are protected?

The dosing claims cover both single-dose and five-day treatment:

Claims	Dosing regimen
27-28	Once daily for one to five days; expressly one day
29	Once daily for five days
31-33	Same regimens for the specific claim 30 formulation
37-38	Once daily for one to five days; expressly five days
53-55	Two or more administrations, including once daily for two to five days and five days

The claims therefore cover a single 65 mg intravaginal application and repeated daily use. The single-dose claims are commercially more closely aligned with Nuvessa’s approved treatment regimen. The five-day claims overlap more closely with traditional metronidazole vaginal-gel treatment patterns.

When does US Patent 8,946,276 lose exclusivity?

The patent term is generally measured from the earliest effective nonprovisional US filing date, subject to patent-term adjustment, terminal disclaimers, and any applicable statutory extensions. Public patent and FDA listing records associate US 8,946,276 with an expiration date in July 2031, commonly reported as July 16, 2031, subject to confirmation from the current USPTO patent-term record and any legal adjustment.

Event	Date or status
Patent issued	February 3, 2015
Patent number	US 8,946,276
Nominal listed expiration	July 16, 2031
Primary product association	1.3% metronidazole vaginal gel
Generic entry before expiration	Dependent on litigation, settlement, licensed entry, or successful invalidity/noninfringement position

Patent expiration does not eliminate FDA regulatory exclusivity, contractual restrictions, or other patents. Conversely, an Orange Book-listed patent does not guarantee that every claim will survive litigation.

What is the FDA and Orange Book status of the protected product?

The claimed product corresponds to Nuvessa, a 1.3% metronidazole vaginal gel approved by FDA for the treatment of bacterial vaginosis in adult females. Nuvessa differs from the older 0.75% metronidazole vaginal gel products in concentration, dose, and dosing schedule.

Product	Active ingredient	Strength	Route	Typical regimen
Nuvessa	Metronidazole	1.3% vaginal gel	Intravaginal	Single administration
MetroGel-Vaginal and generic equivalents	Metronidazole	0.75% vaginal gel	Intravaginal	Usually five days
Clindamycin vaginal products	Clindamycin phosphate	Various	Intravaginal	Product-specific
Solosec	Secnidazole	Oral granules	Oral	Single oral dose

FDA labeling identifies the product as a prescription metronidazole vaginal gel for BV. The Orange Book is the relevant source for listed patents, approved applicant information, dosage form, and generic application status.[1][2]

The product is a small-molecule drug. Biosimilar analysis is therefore not applicable. Any competing application would proceed through the abbreviated new drug application pathway or another small-molecule regulatory route, not through the biosimilar pathway under section 351(k) of the Public Health Service Act.

Which companies are challenging the patent?

A complete Paragraph IV and litigation assessment requires current FDA Orange Book records, ANDA paragraph IV notices, PACER filings, and district-court docket review. The claim text alone does not establish whether a particular manufacturer has filed a Paragraph IV certification or entered litigation.

The likely legal pathway for a generic 1.3% metronidazole vaginal gel would involve:

An ANDA referencing the approved 1.3% product.
A certification concerning listed patents.
A Paragraph IV notice if the applicant contends that a patent is invalid, unenforceable, or not infringed.
Potential litigation under 21 U.S.C. § 355(j)(5)(B)(iii).
A 30-month stay if the statutory conditions are satisfied.

A generic manufacturer targeting only the older 0.75% metronidazole vaginal gel would not necessarily challenge US 8,946,276 because the patent is directed to approximately 1.3% MTZ and approximately 65 mg per application. The main Paragraph IV incentive arises from a product designed to substitute for the 1.3% product.

What patent litigation and settlements affect US 8,946,276?

The supplied record identifies no litigation docket, settlement agreement, covenant not to sue, license, or authorized-generic arrangement. Patent ownership, FDA listing, and litigation status must be separated:

Assignment records establish ownership or recorded interests.
Orange Book records establish listed-product patent status.
Court dockets establish infringement litigation.
Settlement agreements establish authorized entry dates, licenses, or restrictions.
FDA approval records establish regulatory approval, not claim validity.

A settlement could permit generic entry before July 2031 without invalidating the patent. An authorized generic or licensed product could also enter under terms that do not apply to an unlicensed Paragraph IV applicant.

How strong is the patent estate for the 1.3% metronidazole gel?

The estate is strongest against a close substitute that reproduces the commercial product’s key parameters:

1.3 wt% metronidazole;
Approximately 65 mg per dose;
Intravaginal use for BV;
Aqueous gel dosage form;
Absence of the listed excipients;
Mucoadhesive polymer;
Benzyl alcohol, propylene glycol, and PEG 400 solvent system; and
One-dose or short-course administration.

Its limitations are equally clear.

First, the independent claims are use claims. They require treatment of BV and intravaginal administration. A composition-only sale may not satisfy every claim without evidence of intended use.

Second, “about 1.3 wt%” and “about 65 mg” create numerical flexibility but also introduce claim-construction questions. The applicable range depends on intrinsic evidence, prosecution history, formulation variability, and the court’s construction.

Third, claims 2 and 3 rely on specialized testing protocols and comparator formulations. These claims are harder to establish without reproducible testing and access to the specified analytical methods.

Fourth, the negative limitations may be valuable against a close copy but can narrow the claims. A product containing a surfactant, cyclodextrin, niacin, or niacinamide may avoid literal infringement of claims requiring the gel to be “free of” those ingredients.

What generic entry risks exist?

Scenario 1: generic 1.3% single-dose gel

This is the highest-risk scenario. A product matching the 1.3% concentration, 65 mg unit dose, intravaginal route, and BV indication would face direct exposure under claim 39 and potentially claims 1 and 34.

Scenario 2: 0.75% metronidazole gel

This product is less exposed because it does not meet the claimed approximately 1.3 wt% concentration or 65 mg dose. It competes primarily with older metronidazole vaginal-gel products rather than the patented 1.3% product.

Scenario 3: reformulated 1.3% product with a listed excipient

Adding a surfactant, cyclodextrin, niacin, or niacinamide could create a noninfringement position against claims containing the “free of” limitation. That position would depend on whether the ingredient is present in the accused product, its function, and the applicable claim construction.

Scenario 4: alternative route or indication

An oral, rectal, dermatological, or non-BV product generally falls outside the express intravaginal BV-treatment limitations.

Scenario 5: alternative dose or concentration

A materially different concentration or unit dose may avoid literal infringement, but the doctrine of equivalents remains a potential issue. The prosecution history and the significance of the claimed 1.3%/65 mg pairing would be central.

How does Nuvessa compare with older metronidazole vaginal products?

Issue	Nuvessa-type product	Older 0.75% vaginal gel
MTZ concentration	Approximately 1.3%	Approximately 0.75%
Dose	Approximately 65 mg	Product-specific, generally lower concentration
Dosing	Single-dose or short-course claims	Commonly five-day regimen
Patent focus	Formulation, dose, solvent system, mucoadhesion, performance	Earlier metronidazole vaginal-gel technology
Primary patent risk	US 8,946,276 and related family members	Earlier product and formulation patents
Regulatory pathway	NDA product	Generic and legacy product market
Biosimilar relevance	None	None

The patent does not block all metronidazole vaginal therapy. It targets a particular high-concentration, low-volume, mucoadhesive formulation and its use in BV.

Key Takeaways

US 8,946,276 is a method-of-treatment patent centered on approximately 1.3 wt% intravaginal metronidazole gel.
The commercially important dose is approximately 65 mg MTZ per application.
Claim 39 is the central broad-use claim because it omits many narrower polymer, solvent, viscosity, pH, and preservative requirements.
Claims 1 and 34 add aqueous-gel, polymer, performance, and excipient-exclusion limitations.
Claims 30 and 52 define a highly specific formulation using polycarbophil AA-1, benzyl alcohol, propylene glycol, PEG 400, methyl paraben, and propyl paraben.
The estate covers single-dose and repeated daily administration, including five-day regimens.
Public records associate the patent with a July 16, 2031 expiration date, subject to the controlling USPTO term calculation.
A generic 1.3% single-dose vaginal gel presents the highest infringement risk.
A 0.75% metronidazole vaginal gel, a product containing a disclaimed excipient, or a nonintravaginal product has a stronger noninfringement position.
Biosimilar competition is irrelevant because metronidazole is a small molecule.
A definitive Paragraph IV, litigation, settlement, and licensing assessment cannot be derived from the claim text alone.

Frequently Asked Questions

Is US 8,946,276 a composition patent or a method patent?

It is principally a method patent. The claims require treating BV by administering the claimed metronidazole gel intravaginally. The patent does not rely solely on ownership of a free-standing composition claim.

Does the patent cover generic 0.75% metronidazole vaginal gel?

Generally, no. The claims center on approximately 1.3 wt% metronidazole and approximately 65 mg per application. A 0.75% product would normally fall outside those numerical limitations.

Does a 65 mg dose automatically infringe the patent?

No. Dose alone is insufficient. The relevant claim also requires approximately 1.3 wt% MTZ, an intravaginal aqueous gel, treatment of BV, and, for several claims, specified composition or performance characteristics.

Can a reformulated product avoid the patent by using a surfactant?

Potentially. Claims 1, 34, and 39 require the claimed gel to be free of surfactants and certain other excipients. The outcome depends on the ingredient’s actual presence and the construction of “free of.”

Are there biosimilar risks for Nuvessa?

No. Nuvessa contains metronidazole, a small-molecule active ingredient. Competitive products would be regulated as generic or other small-molecule products, not biosimilars.

What is the most important technical issue in an infringement analysis?

The most important issue is whether the accused product matches the combined 1.3 wt% MTZ and approximately 65 mg intravaginal dose limitations. The solvent system, polymer, excipient exclusions, and dosing regimen then determine exposure under the dependent and alternative independent claims.

References

U.S. Food and Drug Administration. (n.d.). Drugs@FDA: FDA-approved drugs and Orange Book patent information. https://www.accessdata.fda.gov/scripts/cder/daf/
U.S. Food and Drug Administration. (n.d.). Nuvessa prescribing information. FDA.
United States Patent and Trademark Office. (2015). U.S. Patent No. 8,946,276, metronidazole vaginal gel. Google Patents/USPTO patent record.
U.S. Food and Drug Administration. (1984). Drug Price Competition and Patent Term Restoration Act, 21 U.S.C. § 355(j).
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations. 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
Alembic Therap	NUVESSA	metronidazole	GEL;VAGINAL	205223-001	Mar 24, 2014		RX	Yes	Yes	8,946,276	⤷ Start Trial				TREATMENT OF BACTERIAL VAGINOSIS WITH METRONIDAZOLE GEL	⤷ 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

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	2012275292	⤷ Start Trial
Australia	2016200825	⤷ Start Trial
Brazil	112013033759	⤷ Start Trial
Canada	2840571	⤷ Start Trial
Canada	3054236	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 8,946,276

Which drugs does patent 8,946,276 protect, and when does it expire?

Summary for Patent: 8,946,276