Details for Patent: 11,324,721

Which drugs does patent 11,324,721 protect, and when does it expire?

Patent 11,324,721 protects SOLOSEC and is included in one NDA.

This patent has sixteen patent family members in five countries.

Summary for Patent: 11,324,721

Title:	Secnidazole for use in the treatment of trichomoniasis
Abstract:	Embodiments are directed to secnidazole formulations and the use of a secnidazole formulation for the treatment of trichomoniasis in a subject in need thereof.
Inventor(s):	Helen S. PENTIKIS, David Palling, Carol J. BRAUN
Assignee:	Evofem Biosciences Inc
Application Number:	US16/890,526
Patent Claim Types: see list of patent claims	Use; Formulation; Delivery;

US Patent 11,324,721: Secnidazole Microgranule Claims, Exclusivity Scope, and Patent Landscape

US Patent 11,324,721 protects treatment of trichomoniasis using a specific oral secnidazole microgranule formulation. The patent does not broadly claim secnidazole, all secnidazole formulations, or all uses of secnidazole. Its enforceable scope depends on the combination of five principal limitations: secnidazole as the sole drug, 400-841 micrometer microgranules, sugar-sphere cores, a secnidazole-containing outer layer, and specified pharmacokinetic results. The dependent claims add a 2-gram dose, oral administration, food vehicles, female and pregnant patients, bacterial vaginosis, single-dose treatment, and contraceptive coadministration.

What does US Patent 11,324,721 claim?

The patent contains three independent method claims and seventeen dependent claims. Claims 1, 2, and 3 are directed to treating trichomoniasis by administering secnidazole in the claimed microgranule formulation.

Claim	Independent limitation	Required pharmacokinetic result
1	Treatment of trichomoniasis with secnidazole microgranules	Cmax of about 34.5-58.3 µg/mL or about 17.4-26.5 µg/mL
2	Same formulation and treatment framework	Tmax of about 2-6 hours
3	Same formulation and treatment framework	Tmax of about 3-4 hours

All three independent claims require the formulation to contain:

1. A plurality of microgranules.
2. Secnidazole in each microgranule.
3. A particle diameter of 400-841 micrometers.
4. A sugar sphere core.
5. An outer layer disposed on the core.
6. Secnidazole in the outer layer.
7. Secnidazole as the sole drug in the formulation.
8. Administration to a subject with trichomoniasis.
9. A therapeutically effective amount producing the applicable Cmax or Tmax result.

The formulation and pharmacokinetic limitations are cumulative. A product that contains secnidazole but lacks the required particle structure, or produces a different pharmacokinetic profile, would not literally satisfy the independent claims.

How narrow is the scope of US Patent 11,324,721?

The patent is narrow in formulation architecture but potentially broad in clinical implementation once the formulation is used.

The claims are method claims, not composition claims

The patent does not directly claim ownership of a secnidazole microgranule product in the abstract. It claims a method of treating trichomoniasis using that product. Direct infringement therefore requires performance of the claimed treatment method, including administration to a patient with trichomoniasis.

A manufacturer could still face indirect infringement exposure if it makes, sells, or promotes a formulation with the claimed structure for the claimed use. The risk depends on the product’s instructions, promotional materials, labeling, and the extent to which the formulation has substantial noninfringing uses.

The particle-size range is a key structural limitation

Each microgranule must have a particle diameter from 400 to 841 micrometers. The claim language refers to each microgranule, not merely an average particle diameter or a population median. That distinction can create a significant infringement and validity issue.

A formulation with a stated D50 of 500 micrometers may not prove that every microgranule falls within the claimed range. Conversely, a formulation with a broad distribution extending outside the range could create a dispute over whether the claim requires all particles to comply or whether ordinary measurement tolerances apply.

The term "about" modifies the pharmacokinetic values, but the particle range is stated without "about." Analytical methods, sampling, sieve classification, and manufacturing tolerances are likely to affect claim interpretation.

The sugar-sphere core and drug-layer arrangement limit design-around options

The microgranule must have a sugar sphere core and an outer layer containing secnidazole. A formulation using a homogeneous matrix granule, a lipid core, a polymeric core, or secnidazole embedded throughout the particle could argue that it lacks the claimed core-layer architecture.

The specification and prosecution history would control whether the claims reach equivalent structures under the doctrine of equivalents. A design using a non-sugar core or a matrix structure may still present litigation risk if it performs substantially the same function in substantially the same way with substantially the same result. The literal claim language, however, favors a structural distinction between a central sugar sphere and an outer secnidazole layer.

What do the pharmacokinetic limitations require?

The pharmacokinetic limitations are central to the patent’s scope and create both enforcement value and litigation complexity.

Claim 1: alternative Cmax windows

Claim 1 covers a method producing either:

• A Cmax of about 34.5-58.3 µg/mL; or
• A Cmax of about 17.4-26.5 µg/mL.

These are alternative limitations. A treatment falling within either range may satisfy the Cmax element, subject to the meaning of "about" and the applicable assay conditions.

The two ranges suggest that the patent may address different subject populations, dosing conditions, or pharmacokinetic cohorts. A generic or competing product could attempt to avoid claim 1 by producing a Cmax outside both windows. That strategy would not automatically avoid claims 2 or 3, which use Tmax rather than Cmax.

Claim 2: broader Tmax range

Claim 2 requires a Tmax of about 2-6 hours. It is broader than claim 3 because the 3-4 hour range falls within the 2-6 hour range.

Claim 3: narrower Tmax range

Claim 3 requires a Tmax of about 3-4 hours. It is a narrower species of claim 2. If claim 3 is invalidated or avoided, claim 2 may still remain relevant for products producing a Tmax outside 3-4 hours but within 2-6 hours.

Why pharmacokinetic limitations create enforcement risk

Tmax and Cmax vary with food intake, patient characteristics, sampling frequency, assay methodology, gastrointestinal conditions, and concomitant medicines. A sponsor seeking to enforce the patent would need reliable evidence that the accused administration method produces the claimed result in the relevant subject population.

The PK limitations also provide a possible noninfringement position. A competitor could argue that its formulation has the required secnidazole and particle structure but does not produce the claimed Cmax or Tmax. That position would depend on clinical and bioequivalence data rather than formulation composition alone.

What do the dependent claims add?

Claims	Added limitation
4	2 grams of secnidazole under claim 1
5	Oral administration
6	Povidone, polyethylene glycol, ethyl acrylate/methyl methacrylate copolymer, talc, or combinations
7-9	Formulation integrated into food, including applesauce, yogurt, or pudding
10	Female subject
11	Pregnant female subject
12, 18, 19	Subject also suffering from bacterial vaginosis
13	Single-dose administration
14-16	Coadministration with ethinyl estradiol, norethindrone, or both, on the same or a different day
17	No effect on contraceptive efficacy of ethinyl estradiol, norethindrone, or both
20	2 grams of secnidazole under claim 2

Claims 4 and 20 are commercially significant because the marketed secnidazole regimen is a 2-gram dose. Claims 7-9 are directed to the patient-use presentation, where the granules are mixed with a soft food vehicle.

Claims 10-12 and 18-19 extend the claimed population to female patients, pregnant females, and patients with bacterial vaginosis. These claims do not remove the requirement that the treatment be for trichomoniasis under the claims from which they depend. Bacterial vaginosis is an added condition, not a replacement for trichomoniasis.

Claims 14-17 address hormonal contraceptive interactions. They can create a separate layer of protection around administration with ethinyl estradiol or norethindrone. Claim 17 is particularly dependent on evidence that contraceptive efficacy is not affected, which may require clinical pharmacology data.

What formulation is associated with these claims?

The claimed formulation corresponds to a multiparticulate oral granule product in which secnidazole is layered onto sugar spheres. The listed excipients indicate a drug-layer and coating system that may include:

• Povidone as a binder;
• Polyethylene glycol as a processing or plasticizing component;
• An ethyl acrylate and methyl methacrylate copolymer as a film-forming or release-control polymer; and
• Talc as an anti-tacking or processing aid.

The patent claims do not require every listed excipient. Claim 6 is a dependent claim requiring at least one listed ingredient. The independent claims can be infringed without the presence of those specific excipients if all independent limitations are otherwise met.

What is the FDA status of the relevant secnidazole product?

The relevant FDA product is Solosec, secnidazole oral granules, marketed by Lupin Pharmaceuticals. FDA approved Solosec under NDA 209363. The product is a 2-gram oral granule formulation used for bacterial vaginosis in adult females and trichomoniasis in adults, according to FDA labeling.[1]

The label directs administration of the granules by sprinkling them onto soft food such as applesauce, pudding, or yogurt and consuming the mixture without chewing or crushing the granules.[1] That administration method corresponds closely to claims 5, 7, and 8.

FDA approval does not itself establish patent validity or infringement. Regulatory approval and patent rights are separate systems. The FDA label can, however, provide evidence relevant to induced infringement, approved use, dose, route of administration, and the commercial formulation.

What is the Orange Book status of US Patent 11,324,721?

The Orange Book determines whether a patent is listed against an approved drug product and whether it carries a method-of-use designation. The patent number alone does not establish its current Orange Book listing, use code, delisting status, or any approved-product exclusivity consequence.

For Solosec, the relevant regulatory questions are:

• Whether US 11,324,721 is listed against NDA 209363;
• Whether the listing is for the product, formulation, or method of use;
• Whether the use code covers trichomoniasis, bacterial vaginosis, or both;
• Whether the listed patent is subject to a Paragraph IV certification; and
• Whether FDA has accepted or approved any abbreviated new drug application referencing the listed patent.

The claims themselves are method-of-use claims. If listed, they would be most likely to generate a method-of-use certification issue rather than a conventional composition-patent challenge.

When does US Patent 11,324,721 lose exclusivity?

US Patent 11,324,721 issued on March 15, 2022. Its expiration date cannot be established from the claims or grant number alone. The controlling date depends on the earliest effective nonprovisional priority date, any terminal disclaimer, patent-term adjustment, and any patent-term extension.

The ordinary statutory framework is a 20-year term measured from the earliest effective US nonprovisional filing date, subject to statutory adjustments.[2] A patent-term extension, if granted for the approved product, could affect the enforceable term. A terminal disclaimer could shorten the term if the patent is tied to an earlier patent in the same family.

The grant date is therefore not the expiration date. A reliable exclusivity analysis must distinguish:

Exclusivity category	Relevance
Patent term	Depends on priority, filing history, terminal disclaimers, and PTA/PTE
FDA orphan exclusivity	Not the principal pathway for Solosec
New chemical entity exclusivity	Relevant to the original FDA approval period, not necessarily to this later patent
Pediatric exclusivity	Could add six months if granted
Orange Book listing	Determines certification and approval timing consequences for ANDA applicants

Which companies are most exposed to this patent?

The primary commercial exposure is for companies developing or marketing an oral secnidazole granule product for trichomoniasis. Risk is highest where the competing product copies the following characteristics:

1. A 2-gram secnidazole dose.
2. Sugar-sphere cores.
3. Secnidazole layered onto the cores.
4. Particle sizes within 400-841 micrometers.
5. Administration on applesauce, yogurt, or pudding.
6. A single oral dose.
7. A PK profile within the claimed Cmax or Tmax ranges.

A tablet, capsule, suspension, or powder formulation may avoid the microgranule limitations. That does not eliminate exposure to other patents covering secnidazole, formulation manufacture, treatment of bacterial vaginosis, or commercial product presentation.

What Paragraph IV challenges could target this patent?

An ANDA applicant could challenge an Orange Book-listed patent through a Paragraph IV certification on several grounds:

Invalidity

Potential invalidity theories could include:

• Lack of novelty based on prior secnidazole formulations;
• Obviousness based on known secnidazole dosing and multiparticulate drug-delivery techniques;
• Lack of written description for the particle-size and PK combinations;
• Lack of enablement across the full range of subjects and administration conditions;
• Indefiniteness involving "about," "therapeutically effective amount," and the measurement of particle diameter; and
• Double patenting if the claims overlap an earlier patent family member.

Noninfringement

A challenger could design around one or more required elements by using:

• A non-sugar core;
• A matrix granule instead of an outer drug layer;
• Particle sizes outside the claimed range;
• A different route or dosage form;
• A different secnidazole dose; or
• A formulation with PK results outside the claimed windows.

A Paragraph IV strategy would need to address all potentially relevant Orange Book-listed patents, not only US 11,324,721.

How strong is the patent estate?

US 11,324,721 has meaningful commercial value because it links a formulation structure to an approved therapeutic use and a defined PK profile. Its strongest features are the alignment between the claims and the marketed product’s 2-gram oral granules, food administration, and female trichomoniasis/BV population.

Its main vulnerabilities are the narrow structural limitations and the PK requirements. The formulation must be shown to contain the claimed architecture, while infringement of the PK limitations may require patient-level or clinical-study evidence. The patent is therefore stronger against a close copy of the marketed product than against a substantially different secnidazole dosage form.

The estate should be assessed as a family rather than by this patent in isolation. Relevant issues include earlier secnidazole formulation patents, continuation applications, method-of-use patents, manufacturing patents, Orange Book listings, terminal disclaimers, and any settlement or license agreements affecting generic entry.

What licensing and litigation issues affect secnidazole competition?

Symbiomix Therapeutics developed Solosec, and Lupin acquired Symbiomix in 2017, obtaining the Solosec business and related intellectual property.[3] Lupin is therefore the principal commercial entity associated with the product and its patent position.

The supplied claims do not establish a Paragraph IV lawsuit, settlement agreement, license to a generic manufacturer, or current litigation status involving US 11,324,721. Those matters are not inferable from claim language. A patent grant also does not establish that a generic applicant has challenged the patent or that a court has upheld it.

What generic launch scenarios are most plausible?

Scenario	Likely strategy	Risk under US 11,324,721
Close-copy granules	2-gram secnidazole layered onto sugar spheres	High
Different multiparticulate core	Non-sugar or matrix-based granules	Lower literal infringement risk
Different particle distribution	Outside 400-841 micrometers	Potentially lower, subject to equivalents
Tablet or capsule	Non-granule dosage form	Lower risk under these claims
Different clinical use	Treatment other than trichomoniasis	Lower risk under the method claims, but other patents may apply
Same structure, different PK	Cmax/Tmax outside claimed ranges	Potential noninfringement position
Authorized generic	License or commercial agreement	Depends on contract terms and Orange Book status

Key Takeaways

• US 11,324,721 is a method-of-treatment patent centered on a specific secnidazole microgranule formulation.
• The independent claims require 400-841 micrometer particles, sugar sphere cores, secnidazole outer layers, and secnidazole as the sole drug.
• Claim 1 uses alternative Cmax ranges. Claims 2 and 3 use overlapping Tmax ranges, with claim 3 narrower than claim 2.
• The dependent claims protect the 2-gram dose, oral administration, soft-food delivery, female and pregnant patients, bacterial vaginosis, single-dose treatment, and hormonal contraceptive coadministration.
• The patent is most relevant to a close generic copy of Solosec oral granules.
• A tablet, capsule, matrix granule, non-sugar core, different particle-size distribution, or different PK profile may provide design-around positions.
• The grant date does not establish expiration. Patent term requires review of priority claims, terminal disclaimers, PTA, PTE, and any pediatric extension.
• Patent listing, Paragraph IV activity, litigation, settlements, and generic launch timing cannot be determined from the claims alone.

FAQs

Does US 11,324,721 cover secnidazole tablets?

No. The claims require a microgranule formulation with 400-841 micrometer particles, sugar sphere cores, and secnidazole in an outer layer. A tablet would not literally satisfy those limitations.

Does the patent cover treatment of bacterial vaginosis alone?

Not under the supplied claims. The independent claims require treatment of trichomoniasis. Claims 12, 18, and 19 add bacterial vaginosis as a coexisting condition.

Is a 2-gram secnidazole dose automatically infringing?

No. The 2-gram dose is only one limitation in dependent claims 4 and 20. The formulation, particle size, sugar core, outer secnidazole layer, sole-drug requirement, trichomoniasis treatment, and applicable PK limitations must also be satisfied.

Can a generic avoid the patent by changing the food vehicle?

Possibly, but not necessarily. Applesauce, yogurt, and pudding are dependent-claim limitations. Avoiding those vehicles would not avoid the broader independent claims if the generic still uses the claimed formulation and administration method.

Is the patent relevant to biosimilar competition?

No. Secnidazole is a small-molecule drug, not a biologic. The relevant competitor pathway is an ANDA or another small-molecule approval route, not a biosimilar application under the Public Health Service Act.

References

1. U.S. Food and Drug Administration. (2023). Solosec (secnidazole) oral granules prescribing information. Lupin Pharmaceuticals, Inc.

2. United States Patent and Trademark Office. (2024). Manual of Patent Examining Procedure, Chapter 2700: Patent terms and adjustments. U.S. Department of Commerce.

3. Lupin Limited. (2017). Lupin acquires Symbiomix Therapeutics and its FDA-approved product Solosec. Corporate announcement.

4. United States Patent No. 11,324,721. (2022). Methods of treating trichomoniasis using secnidazole microgranule formulations. U.S. Patent and Trademark Office.

Drugs Protected by US Patent 11,324,721

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Evofem Inc	SOLOSEC	secnidazole	GRANULE;ORAL	209363-001	Sep 15, 2017		RX	Yes	Yes			Y			TREATMENT OF BACTERIAL VAGINOSIS IN ADULT WOMEN
Evofem Inc	SOLOSEC	secnidazole	GRANULE;ORAL	209363-001	Sep 15, 2017		RX	Yes	Yes			Y			TREATMENT OF TRICHOMONIASIS IN ADULTS
Evofem Inc	SOLOSEC	secnidazole	GRANULE;ORAL	209363-001	Sep 15, 2017		RX	Yes	Yes			Y			TREATMENT OF BACTERIAL VAGINOSIS IN FEMALE PATIENTS 12 YEARS OF AGE AND OLDER
Evofem Inc	SOLOSEC	secnidazole	GRANULE;ORAL	209363-001	Sep 15, 2017		RX	Yes	Yes			Y			TREATMENT OF TRICHOMONIASIS IN PATIENTS 12 YEARS OF AGE AND OLDER

International Family Members for US Patent 11,324,721

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	2015311674
Australia	2018203882
Australia	2018217262
Canada	2959414