US Patent 11,020,377: Secnidazole Microgranule Claims, Exclusivity, Litigation Risk and Generic Entry Analysis

US Patent 11,020,377 protects specific 2-gram, single-dose oral secnidazole microgranule compositions and methods of use. The core limitation is a multiparticulate formulation containing secnidazole, a sphere core, and an ethyl acrylate/methyl methacrylate copolymer, with particle diameters of 400 to 841 micrometers and specified pharmacokinetic performance. The patent is directed to the formulation platform associated with single-dose secnidazole granules rather than to secnidazole as a molecule.

The strongest commercial claims are composition claims 1 and 9, particularly when combined with claims 10-17 and the single-dose pouch or sachet claims 23-26. Method claims 3-8 and 18-22 cover treatment of bacterial vaginosis, including use in pregnant females and administration with applesauce, yogurt or pudding. Claims 27-30 address coadministration with contraceptives. Claims 31-38 extend into STI-risk reduction and trichomoniasis-related methods, but those claims present greater validity and enforcement risk.

What does US Patent 11,020,377 protect?

The patent claims a formulation with the following cumulative elements:

Limitation	Claims principally affected	Commercial significance
Oral pharmaceutical composition	1, 9	Limits the claims to oral delivery
Single dose	1, 9, 23-26	Targets the 2-gram single-administration product
Secnidazole as the sole drug	1, 9	Excludes combination drug compositions within the claimed product
2 grams of secnidazole	1, 9	Narrows the claims to the commercial dose
Plurality of microgranules	1, 9	Covers multiparticulate granule technology
Particle diameter of 400-841 micrometers	1, 9	Creates a measurable product boundary
Ethyl acrylate/methyl methacrylate copolymer	1, 9, 10, 13-15	Covers the principal release-controlling or protective polymer
Sphere or sugar sphere core	1, 9, 11	Defines the multiparticulate architecture
PK performance	1, 9, 16-17	Adds concentration, Tmax or half-life limitations
Bacterial-vaginosis treatment	1, 3, 9, 18	Core therapeutic indication
Female or pregnant female patient	5-6, 19-20	Expands method-of-use coverage
Food administration	7-8, 21-22	Covers administration in applesauce, yogurt or pudding
Pouch or sachet	23-26	Protects a commercially relevant unit-dose presentation
Contraceptive coadministration	27-30	Addresses use with ethinyl estradiol and norethindrone
STI-risk reduction	31-38	Broader, more vulnerable method claims

The claims do not cover every secnidazole product. A product lacking the specified microgranule size, polymer, 2-gram dose, or claimed PK profile may avoid literal infringement, subject to doctrine-of-equivalents analysis.

How do independent claims 1 and 9 differ?

Claims 1 and 9 are parallel composition claims with different structural drafting.

Claim 1: sugar-sphere formulation

Claim 1 requires each microgranule to contain:

Secnidazole;
A sugar sphere;
An ethyl acrylate/methyl methacrylate copolymer; and
A particle diameter between 400 and 841 micrometers.

The composition must contain 2 grams of secnidazole, with secnidazole as the sole drug. It must also meet at least one of the stated PK alternatives:

Maximum plasma concentration at about 3 to 4 hours;
Elimination half-life of about 11.3 to 20.4 hours.

Claim 1 therefore combines structural, dose, particle-size, drug-content and pharmacokinetic requirements.

Claim 9: sphere-core and outer-layer formulation

Claim 9 requires each microgranule to contain:

Secnidazole;
A sphere core;
An outer layer disposed on the sphere core;
An ethyl acrylate/methyl methacrylate copolymer; and
A particle diameter between 400 and 841 micrometers.

Claim 9 includes alternative PK limitations involving:

Maximum plasma concentration of about 34.5 to 58.3 micrograms per milliliter;
Time to maximum plasma concentration of about 2 to 6 hours; or
Elimination half-life of about 11.3 to 20.4 hours.

Unlike claim 1, claim 9 does not itself require the sphere core to be a sugar sphere. That limitation appears in dependent claim 11. Claim 9 also expressly requires an outer layer, creating a formulation-architecture distinction from claim 1.

What formulations are protected by the dependent claims?

Claims 10-17 narrow the outer-layer formulation and pharmacokinetic profile.

Claim 10 requires a coating layer on top of the outer layer. The coating may contain povidone, polyethylene glycol, the acrylate/methacrylate copolymer or talc.

Claim 11 requires a sugar sphere core. Claim 12 requires secnidazole in the outer layer. Claim 13 adds excipients to the outer layer. Claims 14 and 15 specifically require the acrylate/methacrylate copolymer, with claim 15 also requiring polyethylene glycol.

Claim 16 narrows Tmax to approximately 3 to 4 hours. Claim 17 narrows the half-life to approximately 14.7 to 20.4 hours.

These dependent claims create fallback positions if a court invalidates or narrows the broader independent claims. They also increase the likelihood that a commercially optimized formulation will fall within at least one claim combination.

When does US Patent 11,020,377 expire?

US Patent 11,020,377 issued on June 1, 2021. Its expiration date cannot be determined reliably from the claims alone because patent expiration depends on the earliest effective nonprovisional filing date, priority claims, patent-term adjustment, patent-term extension and terminal disclaimers.[1]

Event	Date or status
Patent issued	June 1, 2021
Statutory term	Generally 20 years from the earliest effective nonprovisional filing date
Patent-term adjustment	Not established by the claim text
Patent-term extension	Not established by the claim text
Terminal disclaimer	Not established by the claim text
Exact expiration date	Not determinable from the supplied claims

The issue date is not the expiration date. A later-issued continuation can expire on the same date as an earlier family member if it claims priority to the same application chain.

What is the Orange Book status of US Patent 11,020,377?

The claims supplied do not establish whether US 11,020,377 is listed in the FDA Orange Book for the secnidazole product marketed as Solosec. Orange Book listing is a regulatory record separate from patent issuance. The FDA evaluates whether a listed patent claims the approved drug, its formulation or an approved method of use.[2]

The relevant reference product is Solosec, a 2-gram oral granule product containing secnidazole. FDA approved Solosec for bacterial vaginosis in females and for trichomoniasis in adults, according to the product labeling and approval materials.[3]

If the patent is listed against an applicable NDA, an ANDA applicant may be required to make a Paragraph IV certification for a patent it believes is invalid, unenforceable or not infringed. If the patent is not listed, it may still create litigation risk under 35 U.S.C. § 271(e)(2) if the proposed ANDA product is alleged to infringe.[4]

What Paragraph IV challenges and generic entry risks exist?

A generic applicant seeking approval for a 2-gram secnidazole oral granule product would likely evaluate several design strategies:

Generic strategy	Likely patent risk
Copy the commercial microgranule architecture	High risk under claims 1 and 9
Use the same polymer but different particle size	Potentially avoids literal particle-size infringement
Use a different release polymer	May avoid the central composition limitations
Use a powder, tablet or capsule	May avoid the microgranule and sphere-core limitations
Use a different secnidazole dose	May avoid the 2-gram limitation, but may not be therapeutically substitutable
Use an immediate-release formulation	May avoid the PK and multiparticulate limitations
Use a different PK profile	May avoid a claim requiring the PK limitation, subject to testing
Remove the sugar sphere	May avoid claim 1 and dependent claim 11, but not necessarily claim 9
Market a product for a nonclaimed indication	Does not necessarily avoid composition claims

The most important design-around opportunity is a non-multiparticulate dosage form. A tablet or capsule containing 2 grams of secnidazole would not appear to satisfy the microgranule, sphere-core and particle-size limitations. That product could still face other patents, regulatory substitution barriers or separate method-of-use claims.

The PK limitations may be difficult to use as a reliable design-around. Plasma concentration and half-life vary with study design, population, sampling schedule and analytical method. A generic applicant would need a controlled pharmacokinetic analysis to determine whether its product falls within the claimed ranges.

How strong is the patent estate?

The patent has meaningful formulation strength but a narrower molecular moat.

Strengths

The claims target a commercially practical 2-gram single-dose product.
The 400-841 micrometer particle-size range is objectively measurable.
The claims combine formulation structure with pharmacokinetic outcomes.
The composition claims do not depend on proving a particular clinical treatment step.
The sachet and food-administration claims align with patient-use characteristics.
The polymer and multilayer architecture may be difficult to reproduce without infringement.

Vulnerabilities

Secnidazole itself is not monopolized by these claims.
The particle-size range may be vulnerable to anticipation or obviousness if prior art discloses overlapping granule sizes.
The polymer is a known pharmaceutical excipient class.
PK limitations may be attacked as inherent, result-effective or insufficiently reproducible.
Claims directed to STI-risk reduction may face written-description, enablement, utility and inherency challenges.
Pregnancy-specific claims may be vulnerable if the specification does not provide adequate clinical support for the claimed population.
Claims 27-30 may be difficult to enforce because they concern coadministration with separately administered contraceptives and include a functional contraceptive-efficacy limitation.

The strongest enforcement position is likely against a generic that deliberately copies the commercial 2-gram coated microgranule product. The weakest positions are likely the broad STI-risk-reduction claims and claims dependent on clinical outcomes not directly established by the formulation.

What patent litigation affects secnidazole products?

The supplied material identifies no litigation docket, Paragraph IV notice, settlement agreement or final judgment involving US 11,020,377. Patent issuance alone does not establish that litigation has occurred.

For commercial diligence, relevant litigation questions include:

Whether the patent is listed for the Solosec NDA;
Whether an ANDA applicant has submitted a Paragraph IV certification;
Whether a 30-month stay has been triggered;
Whether the patent owner filed an infringement action within the statutory period;
Whether any settlement permits a licensed or date-certain generic launch;
Whether the patent has been challenged at the Patent Trial and Appeal Board;
Whether a terminal disclaimer links its expiration to another patent.

No biosimilar pathway applies. Secnidazole is a small-molecule drug, so generic competition would proceed through the ANDA pathway rather than the abbreviated biosimilar pathway under section 351(k) of the Public Health Service Act.[5]

How do the patent claims compare with the FDA-approved product?

The claim set closely tracks the commercial characteristics of single-dose oral secnidazole granules:

Product characteristic	Claimed in US 11,020,377	Solosec product profile
Secnidazole	Yes	Yes
2-gram dose	Yes	Yes
Oral granules	Yes, through microgranules	Yes
Single administration	Yes	Yes
Food-compatible administration	Yes	Product labeling supports administration with soft food
Bacterial vaginosis use	Yes	Yes
Trichomoniasis-related use	STI claims and treatment claims	FDA-approved trichomoniasis indication
Sachet presentation	Claims 23-26	Commercially relevant
Female/pregnancy use	Claims 5, 6, 19 and 20	Label and regulatory support must be assessed separately

The claims should not be treated as a substitute for the FDA label. Patent scope and FDA-approved indication are separate inquiries. A claim can cover a method beyond the approved label, while a labeled use can remain outside a particular patent claim.

What revenue exposure does the patent create?

The commercial exposure is concentrated in a single-dose oral granule product. A generic entrant that copies the microgranule technology could compete directly with the reference product for bacterial vaginosis and trichomoniasis prescriptions. A successful design-around using a tablet, capsule or different multiparticulate system could reduce patent exposure while still threatening the branded product commercially.

The patent is therefore more significant as a product-formulation barrier than as a broad secnidazole exclusivity right. It does not prevent all secnidazole products. It increases the cost and technical complexity of developing a substitutable 2-gram oral granule product.

Key Takeaways

US 11,020,377 protects specific 2-gram secnidazole microgranule formulations, not secnidazole generally.
Claims 1 and 9 are the principal composition claims.
The critical limitations are microgranules, a 400-841 micrometer particle size, an ethyl acrylate/methyl methacrylate copolymer and defined PK performance.
Claims 23-26 add commercially relevant pouch and sachet coverage.
Claims involving pregnancy, contraception and STI-risk reduction are broader in use but more exposed to validity challenges.
A tablet, capsule, powder or formulation using a different polymer may provide a credible design-around.
Exact patent expiration cannot be calculated from the claim text alone.
The supplied information does not establish Orange Book listing, Paragraph IV litigation or a settlement agreement.
Secnidazole is a small molecule; biosimilar risk is not applicable.
The primary generic-entry risk is a copied 2-gram oral granule product rather than every potential secnidazole dosage form.

FAQs

Does US 11,020,377 cover all 2-gram secnidazole products?

No. The claims require specific microgranule structures, particle sizes, polymers and, in several claims, pharmacokinetic characteristics.

Can a secnidazole tablet avoid US 11,020,377?

A tablet would generally have a strong argument that it lacks the claimed plurality of microgranules, sphere core and 400-841 micrometer particle-size range. Other patents or regulatory requirements could still apply.

Does the patent cover secnidazole for trichomoniasis?

Claims 31-38 address STI-risk reduction and trichomoniasis-related methods. The supplied claims do not provide a conventional treatment claim specifically directed to trichomoniasis comparable to the bacterial-vaginosis treatment claims.

Is a generic secnidazole product automatically blocked until the patent expires?

No. A generic applicant may challenge the patent, design around it, establish noninfringement, or resolve the dispute through litigation or settlement.

Does coadministration with oral contraceptives create a separate patent risk?

Yes. Claims 27-30 cover coadministration with ethinyl estradiol, norethindrone or both, including a limitation that contraceptive efficacy is not affected. The enforceability of those claims depends on their construction and evidentiary support.

References

United States Patent and Trademark Office. (n.d.). Patent term adjustment and patent term calculation. https://www.uspto.gov/patents/laws/patent-term-adjustment
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.fda.gov/drugs/drug-approvals-and-databases/approved-drug-products-therapeutic-equivalence-evaluations-orange-book
U.S. Food and Drug Administration. (2017). Solosec (secnidazole) oral granules prescribing information. https://www.accessdata.fda.gov/drugsatfda_docs/label/
United States Code. (2024). 35 U.S.C. § 271(e)(2). https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim-title35-section271
U.S. Food and Drug Administration. (n.d.). Biosimilars and interchangeable biosimilars. https://www.fda.gov/drugs/therapeutic-biologics-applications-bla/biosimilars and interchangeable biosimilars

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	11,020,377	⤷ Start Trial	Y			TREATMENT OF TRICHOMONIASIS IN PATIENTS 12 YEARS OF AGE AND OLDER	⤷ Start Trial
Evofem Inc	SOLOSEC	secnidazole	GRANULE;ORAL	209363-001	Sep 15, 2017		RX	Yes	Yes	11,020,377	⤷ Start Trial	Y			TREATMENT OF BACTERIAL VAGINOSIS IN FEMALE PATIENTS 12 YEARS OF AGE AND OLDER	⤷ Start Trial
Evofem Inc	SOLOSEC	secnidazole	GRANULE;ORAL	209363-001	Sep 15, 2017		RX	Yes	Yes	11,020,377	⤷ Start Trial	Y			TREATMENT OF TRICHOMONIASIS IN ADULTS	⤷ Start Trial
Evofem Inc	SOLOSEC	secnidazole	GRANULE;ORAL	209363-001	Sep 15, 2017		RX	Yes	Yes	11,020,377	⤷ Start Trial	Y			TREATMENT OF BACTERIAL VAGINOSIS IN ADULT WOMEN	⤷ 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	2015311674	⤷ Start Trial
Australia	2018203882	⤷ Start Trial
Australia	2018217262	⤷ Start Trial
Canada	2959414	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 11,020,377

Which drugs does patent 11,020,377 protect, and when does it expire?

Summary for Patent: 11,020,377