US Patent 10,925,833: Claim Scope, Exclusivity, Litigation Risk, and Pyridostigmine Patent Landscape

US Patent 10,925,833 covers a once-daily, gastroretentive pyridostigmine dosage form designed to remain in the stomach for at least 14 hours. The independent claims require a narrow combination of: pyridostigmine, hypromellose, an acid, a carbonate or bicarbonate gas generator, and a permeable elastic membrane based on a specific three-monomer copolymer. The patent also covers an immediate-release pyridostigmine layer, rapid swelling, gastric flotation, tablet dimensions, and selected plasticizers.

The principal infringement risk is highest for a product that reproduces the claimed polymer membrane and gas-generating, swellable core. A conventional sustained-release pyridostigmine tablet without the claimed gastroretentive architecture would generally present a materially different claim profile.

What does US Patent 10,925,833 claim?

The patent has three independent claims: claims 1, 11, and 15. Each requires a gastroretentive dosage form, but the claims differ in product architecture.

Claim	Independent subject matter	Main additional limitations
1	Gastroretentive dosage form with a core and permeable elastic membrane	50-400 mg pyridostigmine; hypromellose; acid; carbonate or bicarbonate; specified copolymer; 14-hour extended release
11	Dosage form with immediate-release and extended-release components	Immediate-release layer contains 10-60 mg pyridostigmine; extended-release component incorporates the claim 1 architecture
15	Gastroretentive tablet	Adds tablet geometry, rapid swelling, gastric retention, and 14-hour release requirements

The independent claims are cumulative. A potentially infringing product must satisfy every limitation of the relevant claim, either literally or under the doctrine of equivalents. A product that omits one required component or falls outside a quantitative range may avoid literal infringement, although the legal outcome would depend on claim construction, prosecution history, and equivalence analysis.[1]

What formulation components are protected?

The claims protect a specific multilayer drug-delivery system rather than pyridostigmine generally.

Pyridostigmine drug load

Claims 1, 3, 11, and 15 require approximately 50 mg to 400 mg of pyridostigmine or a pharmaceutically acceptable salt. Claim 3 specifically identifies pyridostigmine bromide.

Claim 2 and claim 11 separately require an immediate-release amount of approximately 10 mg to 60 mg. The claimed product may therefore deliver an initial pyridostigmine dose followed by prolonged release from the gastroretentive component.

The range is important for freedom-to-operate analysis. A product containing less than 50 mg or more than 400 mg in the extended-release core would not fall literally within that limitation. A product containing 50 mg to 400 mg in the core but using a different total dose could still implicate the claims.

Hydrophilic swelling polymer

The claims require hypromellose as the swellable, water-soluble hydrophilic polymer. Claim 10 and claim 14 specify approximately 5 wt% to 40 wt% hypromellose based on total core weight.

This limitation narrows the claims against formulations based solely on polyethylene oxide, polyvinyl alcohol, carbomer, or other swelling polymers. A formulation containing hypromellose together with another polymer could still satisfy the claims if hypromellose performs the claimed polymer role and falls within the relevant composition.

Acid and gas-generating system

The core must contain an acid and a gas-generating agent. The acid must be selected from:

Succinic acid
Citric acid
Acetic acid
Malic acid
Fumaric acid
Stearic acid
Tartaric acid
Boric acid
Benzoic acid
Mixtures of those acids

The gas-generating agent must be a carbonate salt, bicarbonate salt, or mixture of the two. The acid-carbonate system supports carbon dioxide generation, buoyancy, and expansion in gastric fluid.

A formulation using a nonlisted acid presents a potential design-around position, subject to any broader construction of the Markush language or equivalence theory. A formulation using a non-carbonate gas-generation mechanism, such as a mechanically buoyant low-density matrix without effervescence, also may avoid the literal gas-generator limitation.

Permeable elastic membrane

The membrane must contain at least one orifice and surround the core. It must include:

A copolymer based on ethyl acrylate, methyl methacrylate, and trimethylammonioethyl methacrylate chloride in a 1:2:0.2 ratio;
Approximately 70 wt% to 95 wt% of that copolymer in the membrane composition; and
Approximately 5 wt% to 25 wt% plasticizer.

This polymer is associated with ammonio methacrylate copolymer systems used to form permeable, pH-responsive or water-permeable pharmaceutical coatings. The claimed monomer ratio and membrane concentration are central limitations, not incidental formulation preferences.

Claim 8 lists the permitted plasticizers:

Triethyl citrate
Triacetin
Polyethylene glycol
Propylene glycol
Dibutyl sebacate

A competing product that uses a different membrane polymer, a different monomer ratio, or a plasticizer outside the listed group may have a stronger noninfringement position. The risk increases where the alternative is functionally and compositionally close to the claimed membrane.

How do claims 1, 11, and 15 differ?

Claim 1: broadest core architecture

Claim 1 is the principal composition claim. It covers a gastroretentive dosage form with the required drug, core excipients, membrane, orifice, polymer ratio, plasticizer range, and 14-hour extended-release performance.

Its breadth lies in the absence of a required immediate-release layer and the absence of the specific tablet dimensions in claim 15.

Claim 11: immediate-release plus extended-release product

Claim 11 covers a dosage form with both:

An immediate-release layer containing approximately 10 mg to 60 mg pyridostigmine; and
An extended-release component having the same core-and-membrane architecture.

This claim creates a separate risk category for bilayer tablets, coated gastroretentive systems, and dosage forms with an immediate-release overcoat. A product may avoid claim 11 by omitting the immediate-release layer while still falling within claim 1.

Claim 15: dimensional and performance limitations

Claim 15 is directed to a gastroretentive tablet having:

A long axis of approximately 12 mm to 22 mm;
A short axis of approximately 8 mm to 11 mm;
Swelling within approximately 60 minutes;
A size that prevents passage through the pyloric sphincter; and
At least 14 hours of extended pyridostigmine release.

The dimensions narrow the claim but may create practical infringement risk because many large, oblong gastroretentive tablets could fall within the stated range.

What performance characteristics must a product have?

The claims contain functional limitations tied to gastric behavior.

Performance limitation	Relevant claims
Extended release for at least approximately 14 hours	1, 11, 15
Swelling within approximately 60 minutes or less	4, 12, 15
Size prevents passage through pyloric sphincter	4, 12, 15
Floating within approximately 30 minutes or less	5, 13
Integrity maintained in swollen state for at least approximately 14 hours	6
Single-tablet, once-daily administration	9
Wicking agent in the core	7

Claims 4 through 6 and 12 through 13 are narrower dependent claims. They are potentially important in litigation because they tie infringement to measurable in vitro or in vivo performance. The patent holder would likely rely on dissolution, swelling, flotation, gastric-retention, and tablet-integrity testing to establish these limitations.

The term "about" introduces customary claim-construction flexibility. The scope of that flexibility would depend on the specification, examples, measurement methods, and prosecution record.

What patents protect pyridostigmine extended-release products?

US Patent 10,925,833 protects a gastroretentive delivery platform specifically adapted for pyridostigmine. It does not, based on the supplied claims, broadly claim:

Pyridostigmine as an active ingredient;
All extended-release pyridostigmine tablets;
All pyridostigmine bromide formulations;
All once-daily pyridostigmine products;
Conventional hydrophilic matrix tablets; or
Any formulation containing hypromellose.

The patent’s commercial relevance depends on whether the target product uses the claimed combination rather than merely the same active ingredient and dosing frequency.

The relevant adjacent patent categories are:

Patent category	Relevance to US 10,925,833
Conventional sustained-release pyridostigmine	Potentially prior-art and competitive, but not necessarily within the claims
Gastroretentive floating systems	Relevant to validity and design-around analysis
Swellable expandable dosage forms	Relevant to the gastric-retention mechanism
Ammonio methacrylate copolymer coatings	Relevant to membrane composition and prior art
Pyridostigmine immediate-release formulations	Relevant to claim 11 but generally outside the extended-release core limitations
Manufacturing processes	May create separate process-patent barriers not visible in the supplied claims
Method-of-use patents	May cover dosing or treatment of myasthenia gravis independently of the formulation claims

A complete family-level landscape requires review of the patent’s priority chain, related US continuations and divisionals, international publications, terminal disclaimers, prosecution history, and cited and citing references. Those relationships cannot be established from the claim text alone.

When does US Patent 10,925,833 lose exclusivity?

The grant date alone does not establish the expiration date. Under US patent law, a utility patent generally expires 20 years from the earliest effective nonprovisional US or international filing date, subject to patent-term adjustment, patent-term extension, terminal disclaimers, and other statutory conditions.[2]

Exclusivity issue	Assessment
Patent grant	US 10,925,833
Grant date	February 23, 2021
Ordinary term endpoint	Based on earliest effective nonprovisional filing date, not grant date
PTA	Must be checked in the issued patent and USPTO records
PTE	Not established from the supplied claims
Terminal disclaimer	Must be checked in the prosecution file
Regulatory exclusivity	Separate from patent term and must be checked against the relevant NDA
Orange Book listing	Cannot be inferred from the claims

The patent may retain enforceable claims even if the underlying product has no current FDA regulatory exclusivity. Conversely, FDA exclusivity may expire before the patent.

What is the Orange Book status?

The Orange Book lists patents submitted by NDA holders for approved drug products and identifies certain patent-use codes and expiration information.[3] Patent 10,925,833 cannot be classified as Orange Book-listed solely from its claims.

If the patent is listed against an approved pyridostigmine NDA, a generic applicant could face a Paragraph IV certification. If it is not listed, the patent may still be enforceable but would not necessarily trigger the Orange Book notice and 30-month-stay framework associated with a Paragraph IV certification.

The product-specific questions are:

Whether the patent was submitted to FDA for a pyridostigmine NDA;
Which NDA and dosage form are identified;
Whether FDA accepted the listing;
Whether the listing includes a method-of-use code;
Whether the listed claims cover the proposed generic product; and
Whether the patent has expired or been delisted.

What Paragraph IV and generic-launch risks exist?

A generic applicant pursuing an abbreviated new drug application could challenge the patent through a Paragraph IV certification if the patent is listed for the reference product.[4] The principal invalidity and noninfringement arguments would likely focus on:

Anticipation

The challenger would need a single prior-art reference disclosing every limitation, including the specific membrane copolymer, plasticizer range, hypromellose core, acid, carbonate or bicarbonate gas generator, orifice, pyridostigmine quantity, and 14-hour release requirement.

The combination of composition and performance limitations may make anticipation more difficult than a challenge against a simple sustained-release tablet claim.

Obviousness

An obviousness challenge could combine prior art on:

Pyridostigmine extended release;
Expandable gastric-retentive dosage forms;
Effervescent buoyancy systems;
Hypromellose matrices; and
Permeable ammonio methacrylate membranes.

The strongest challenge would need evidence that a skilled formulation scientist had a reasonable expectation of achieving the claimed 14-hour release, rapid swelling, gastric retention, and structural integrity with the specified polymer and excipient ranges.[5]

Noninfringement

A generic could pursue a formulation that:

Uses a nonlisted membrane polymer;
Omits the orifice;
Uses a nonlisted acid;
Uses a non-carbonate gas-generating system;
Uses a different hydrophilic polymer;
Places pyridostigmine outside the claimed core range;
Does not include the claimed immediate-release layer; or
Uses a conventional non-gastroretentive dosage form.

A product that uses the same membrane polymer and core chemistry but changes only tablet shape or dose may remain exposed under claims 1 or 11.

Which companies are challenging the patent?

The supplied information does not identify any Paragraph IV filer, ANDA applicant, district-court action, Patent Trial and Appeal Board proceeding, settlement, or license involving US 10,925,833. The claim text alone cannot establish current litigation or challenger identity.

The relevant public records for litigation and challenge analysis are:

USPTO Patent Center for prosecution and maintenance records;
FDA Orange Book for listed patents and reference products;
PACER and district-court dockets for Hatch-Waxman litigation;
PTAB records for inter partes review or post-grant review; and
SEC filings and licensing disclosures from involved companies.

No litigation, settlement, or licensing conclusion should be drawn solely from the issued claims.

How strong is the patent estate?

At the claim level, the patent has moderate technical specificity and potentially meaningful product coverage.

Strength factor	Assessment
Technical specificity	High
Breadth over all pyridostigmine ER products	Low
Coverage of the claimed gastroretentive platform	High
Dependence on performance testing	Material
Design-around potential	Moderate
Vulnerability to combination prior art	Moderate
Importance of prosecution history	High
Manufacturing-process coverage	Not shown in supplied claims
Method-of-use coverage	Not shown in supplied claims
Biosimilar relevance	None for this small-molecule product

The patent is strongest against a product intentionally designed to reproduce the claimed architecture. It is weaker against a conventional matrix tablet, a non-effervescent gastroretentive system, or a formulation using a different membrane technology.

What manufacturing and geographic barriers matter?

The claims are composition and dosage-form claims. They do not, based on the supplied text, expressly claim:

Coating-process parameters;
Orifice-formation methods;
Tablet compression conditions;
Granulation methods;
Specific manufacturing equipment;
In-process controls; or
A particular manufacturing site.

A manufacturer could still face separate process or formulation patents in the same family or in related portfolios. Geographic protection is jurisdiction-specific. US Patent 10,925,833 does not itself establish protection in Europe, Canada, Japan, India, or other markets. Foreign counterparts must be reviewed independently for claim scope, prosecution amendments, grant status, and expiration.

Key Takeaways

US Patent 10,925,833 targets a specific gastroretentive pyridostigmine platform, not pyridostigmine generally.
The critical limitations are the hypromellose-containing core, acid-carbonate or bicarbonate gas-generation system, orificed elastic membrane, specified ammonio methacrylate copolymer, plasticizer range, and 14-hour release.
Claims 1, 11, and 15 provide separate coverage for the basic gastroretentive system, an immediate-release/extended-release combination, and a dimensionally defined tablet.
Conventional sustained-release pyridostigmine products may avoid the claims if they lack the gastroretentive membrane and effervescent swelling architecture.
Patent expiration cannot be calculated from the grant date alone.
Orange Book listing, Paragraph IV activity, litigation, settlements, licenses, and current challengers are not established by the supplied claim text.
The patent presents the greatest launch risk for a generic or branded competitor using the same membrane polymer, hypromellose core, carbonate/bicarbonate gas system, and once-daily gastroretentive design.

FAQs

Does US Patent 10,925,833 cover Mestinon Timespan?

The claims do not automatically cover every extended-release pyridostigmine product. Coverage depends on whether the product has the claimed gastroretentive core, hypromellose, acid, carbonate or bicarbonate gas generator, and specified permeable elastic membrane.

Can a pyridostigmine generic avoid the patent by using a conventional matrix tablet?

Potentially. A conventional hydrophilic matrix tablet that does not swell to block the pyloric sphincter, float through gas generation, and use the claimed membrane may avoid the independent claims.

Is pyridostigmine bromide specifically required?

No. The independent claims generally cover pyridostigmine or a pharmaceutically acceptable salt. Claim 3 specifically narrows the formulation to pyridostigmine bromide.

Does changing the plasticizer avoid infringement?

Not necessarily. Claim 1 requires a plasticizer but does not limit the independent claim to the five plasticizers listed in dependent claim 8. A different plasticizer may avoid claim 8 while still potentially falling within claim 1.

Are biosimilar rules relevant to this patent?

No. Pyridostigmine is a small-molecule active ingredient. Generic-drug and Hatch-Waxman procedures, rather than biosimilar procedures under the Biologics Price Competition and Innovation Act, are the relevant regulatory framework.

References

United States Patent and Trademark Office. (2021). U.S. Patent No. 10,925,833.
35 U.S.C. §§ 154, 156.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book.
21 U.S.C. § 355(j); 21 C.F.R. § 314.94.
35 U.S.C. § 103.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Amneal	PYRIDOSTIGMINE BROMIDE	pyridostigmine bromide	TABLET, EXTENDED RELEASE;ORAL	217604-001	Oct 4, 2024		DISCN	No	No	10,925,833	⤷ 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

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Canada	3031412	⤷ Start Trial
Canada	3061382	⤷ Start Trial
China	110996922	⤷ Start Trial
Denmark	3609472	⤷ Start Trial
Denmark	3648747	⤷ Start Trial
Denmark	3824881	⤷ Start Trial
European Patent Office	3609472	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 10,925,833

Which drugs does patent 10,925,833 protect, and when does it expire?

Summary for Patent: 10,925,833