US Patent 7,947,739: Tranexamic Acid Extended-Release Formulation Claims and Patent Landscape

US Patent 7,947,739 protects a 650-mg tranexamic acid tablet with a specific hydrophilic polymer matrix and controlled dissolution profile. The strongest practical coverage centers on hydroxypropylmethylcellulose, or HPMC, at approximately 10% to 35% by weight, combined with release of less than 70% of the drug at 45 minutes and approximately 100% by 120 minutes. The patent also includes narrower pharmacokinetic limitations involving Cmax and Tmax.

The patent covers formulation architecture and performance, not tranexamic acid as an active ingredient. A conventional immediate-release tranexamic acid tablet, an injectable product, or a formulation outside the claimed dissolution and polymer ranges would generally fall outside the literal scope of the principal claims.

What drug and formulation does US Patent 7,947,739 protect?

US 7,947,739 is directed to modified-release tranexamic acid tablets. The patent claims are aligned with the formulation used for Lysteda, the FDA-approved 650-mg oral tranexamic acid product for cyclic heavy menstrual bleeding. The patent specification and claims identify a matrix-tablet approach using cellulose-based release-modifying polymers.

The core protected product has these elements:

Element	Claim requirement
Active ingredient	Tranexamic acid or a pharmaceutically acceptable salt
Dosage form	Tablet
Dose	Approximately 650 mg tranexamic acid per tablet
Release material	Hydroxyalkylcellulose, alkylcellulose, cellulose ether, partial ester, or mixture
Polymer concentration	Approximately 10% to 35% by formulation weight
Key dissolution test	USP 27 Apparatus II, paddle, 50 rpm, 900 mL water, 37 ± 0.5°C
Primary release limitation	Less than approximately 70% released at 45 minutes
Terminal release limitation	Approximately 100% released by 120 minutes
Narrow polymer embodiment	HPMC
Narrow concentration embodiment	Approximately 15% HPMC
Optional dosage form detail	Matrix tablet with pregranulated drug mixed with release material
Optional PK limitations	Specified Cmax and Tmax ranges

The claims do not require a particular brand of HPMC, a particular tablet weight, a specific manufacturing equipment platform, or a particular excipient outside the recited release-modifying polymer.

How many independent claims does US 7,947,739 have?

The patent has four principal independent formulation claims: claims 1, 11, 16, and 18.

Independent claim	Primary scope	Principal limitation
Claim 1	Broad modified-release tranexamic acid tablet	Polymer class, 10%-35% concentration, dissolution profile, 650-mg dose
Claim 11	Alternative dissolution-defined tablet	10%-25% release during each 15-minute interval and complete release by 120 minutes
Claim 16	HPMC-specific formulation	HPMC at 10%-35%, primary dissolution profile, 650-mg dose
Claim 18	HPMC-specific version of claim 11	HPMC at 10%-35%, interval release profile, 650-mg dose

Claims 1 and 11 provide the broadest formulation coverage because they encompass multiple cellulose-based polymers. Claims 16 and 18 are narrower but may be easier to prove against a product that uses HPMC.

A product that satisfies any one independent claim, together with all of that claim's limitations, may infringe even if it does not satisfy the other independent claims.

What does claim 1 cover?

Claim 1 is a product claim directed to a 650-mg tranexamic acid tablet containing a modified-release polymer. It requires all of the following:

Tranexamic acid or a pharmaceutically acceptable salt.
A tablet formulation.
A polymer selected from the specified cellulose-based groups.
Polymer concentration of approximately 10% to 35% by weight.
Less than approximately 70% drug release at 45 minutes.
Approximately 100% drug release by 120 minutes.
Approximately 650 mg tranexamic acid per tablet.

Claim 1 is not limited to HPMC. It can reach formulations using hydroxyalkylcellulose, alkylcellulose, cellulose ethers, partial esters, or mixtures of those materials.

The claim is also performance-limited. A formulation with the correct ingredients and concentration may avoid literal infringement if its measured dissolution profile does not meet the required release parameters. Conversely, a formulation using a different commercial grade of cellulose polymer may still create risk if the material falls within the claimed polymer categories and the dissolution results satisfy the claim.

What does claim 11 cover?

Claim 11 uses a different dissolution limitation. It requires release of approximately 10% to 25% of tranexamic acid every 15 minutes, with approximately 100% release by 120 minutes.

This language creates a potential claim-construction issue. The phrase "every 15 minutes" may be interpreted as a cumulative release profile measured at 15-minute intervals or as release occurring within successive 15-minute periods. The patent specification, prosecution history, and laboratory protocol would be important in determining the correct interpretation.

Claim 11 also requires:

A tablet;
Tranexamic acid or an acceptable salt;
A listed modified-release polymer;
Polymer concentration of approximately 10% to 35%;
Approximately 650 mg per tablet.

A competitor could challenge claim 11 by disputing the meaning of "every 15 minutes," the interpretation of "effective amount," or the reproducibility of the dissolution result.

How do claims 16 and 18 narrow the patent scope?

Claims 16 and 18 limit the release polymer to HPMC.

Claim 16 requires HPMC at approximately 10% to 35% by weight and uses the claim 1 dissolution profile. Claim 18 requires HPMC in the same concentration range and uses the claim 11 interval-release profile.

Claims 17 and 19 narrow the concentration to approximately 15% HPMC. These are commercially significant dependent claims because a formulation using HPMC at 15% is directly within the most specific claim set if the dose and dissolution limitations are also met.

Claim	Polymer	Polymer range	Release test
1	Multiple cellulose-based polymers	10%-35%	<70% at 45 minutes; about 100% at 120 minutes
5	HPMC	10%-35% through dependency	Claim 1 profile
6	Listed polymer	About 15%	Claim 1 profile
7	HPMC	About 15%	Claim 1 profile
16	HPMC	10%-35%	Claim 1 profile
17	HPMC	About 15%	Claim 1 profile
18	HPMC	10%-35%	Claim 11 profile
19	HPMC	About 15%	Claim 11 profile

What formulations are protected by the HPMC claims?

The HPMC claims potentially cover a matrix tablet containing:

Approximately 650 mg tranexamic acid;
Approximately 10% to 35% HPMC;
A release profile below approximately 70% at 45 minutes;
Complete or nearly complete release by 120 minutes.

The claims do not expressly require a particular HPMC viscosity grade. That creates potential breadth across low-, medium-, and high-viscosity HPMC grades, subject to the polymer identity and dissolution requirements.

The claims also do not require the formulation to contain only HPMC as the release material. A product containing HPMC together with other excipients may remain within claims 16 or 18 if HPMC is present at the specified concentration and the complete claim limitations are met.

How important are the dissolution limitations to infringement?

The dissolution limitations are central. They distinguish the claimed product from both immediate-release tranexamic acid and substantially slower extended-release systems.

The required method is specific:

USP 27 Apparatus Type II;
Paddle method;
50 rpm;
900 mL water;
37 ± 0.5°C.

A reliable infringement analysis would require testing the accused product under materially identical conditions. Variables that can affect the result include:

Paddle alignment and vessel geometry;
Water pH and ionic content;
Tablet storage conditions;
Sampling timing;
Filtration;
Assay method;
Agitation speed;
Tablet hardness and compression force;
HPMC grade and particle size;
Granulation sequence.

The "about" language gives the patentee some tolerance, but it does not eliminate the need to establish that the formulation falls within the claimed numerical ranges. A product releasing 72% at 45 minutes may present a materially different position from one releasing 69%, although the legal result would depend on claim construction and prosecution history.

What do the pharmacokinetic claims cover?

Claims 8 through 10 and 12 through 13 add pharmacokinetic limitations to the formulation.

Claim	PK limitation
8	Single 1,300-mg dose produces mean Cmax of about 9-14.5 mcg/mL
9	1,300 mg three times daily produces mean steady-state Cmax of about 12.5-25 mcg/mL
10	Mean Tmax of about 2-3.5 hours
12	Multiple-dose Cmax of about 10-20 mcg/mL
13	Single-dose Cmax of about 9-17.5 mcg/mL

These claims are formulation claims with functional or performance characteristics. They create narrower fallback positions, but they also create proof issues. PK values can vary with:

Food intake;
Subject population;
Renal function;
Sampling schedule;
Bioanalytical method;
Dose administration;
Study design;
Statistical treatment.

A generic applicant could avoid these claims if its product does not produce the specified mean PK result. That does not necessarily avoid claims 1, 11, 16, or 18, which rely principally on composition, dose, and dissolution.

When did US Patent 7,947,739 lose exclusivity?

The patent's enforceability depends on its adjusted expiration date, any terminal disclaimer, maintenance-fee status, and applicable patent-term extension or pediatric exclusivity. The underlying patent record identifies the patent as a U.S. formulation patent issued in 2011, with the statutory term calculated from the relevant nonprovisional filing and priority history. The patent's term should be determined from the USPTO Patent Center record and the FDA Orange Book entry rather than from the issue date alone (U.S. Patent and Trademark Office, n.d.; FDA, 2024a).

The commercial exclusivity analysis has separate components:

Exclusivity type	Relevance to this product
Patent exclusivity	Depends on the live patent term and enforceability
New chemical entity exclusivity	Not available for tranexamic acid, an established active ingredient
Three-year clinical-investigation exclusivity	Could apply to the approved modified-release product if statutory requirements were met
Pediatric exclusivity	Applies only if FDA granted a six-month extension based on a qualifying study
Orphan exclusivity	Not the principal exclusivity mechanism for Lysteda

FDA approval of Lysteda occurred in 2009. The product was approved under an NDA, not as a biologic. Generic competition proceeds through the ANDA pathway, and biosimilar law is not applicable (FDA, 2009; FDA, 2024b).

What is the Orange Book status of US 7,947,739?

The Orange Book is the controlling FDA source for patents submitted for approved drug products. An Orange Book listing can identify the patent number, patent-use code, and expiration information, but it does not decide infringement or validity (FDA, 2024a).

For a tranexamic acid 650-mg tablet:

The relevant listed patent is associated with the Lysteda NDA;
The listed patent relates to the formulation rather than tranexamic acid generally;
The listed use code and expiration information must be matched to the specific NDA product and strength;
A generic applicant may file a Paragraph IV certification against a listed patent or use a Paragraph III certification if it accepts delayed approval until patent expiration.

Orange Book listing does not establish that every 650-mg tranexamic acid tablet infringes. It identifies the patent information submitted by the NDA holder.

Which companies are challenging the Lysteda patent?

Publicly available FDA and patent records should be used to identify ANDA applicants and Paragraph IV notices. An ANDA applicant's identity is not always fully visible in the Orange Book, and Paragraph IV litigation may be filed under a different caption from the product brand.

The relevant competitive set includes manufacturers seeking approval for:

Tranexamic acid tablets;
The 650-mg strength;
An indication that may overlap with heavy menstrual bleeding;
An immediate-release or modified-release dosage form.

An immediate-release generic tranexamic acid tablet may compete clinically without necessarily practicing the patented modified-release formulation. A product seeking AB-rated substitution for Lysteda presents a closer patent and regulatory issue because it may need to match the reference product's dosage form, strength, and labeling pathway.

A complete Paragraph IV determination requires review of FDA ANDA litigation records, district court dockets, and any Federal Circuit decisions. The patent itself does not identify all commercial challengers.

What patent litigation affects tranexamic acid tablets?

The principal litigation risks arise from four issues:

Whether an ANDA product meets the dissolution limitations.
Whether its polymer falls within the claimed cellulose categories.
Whether the 650-mg dose is present on an active-ingredient basis or salt-equivalent basis.
Whether the patent remains enforceable when the generic is ready to launch.

The likely litigation evidence would include:

ANDA formulation documents;
Batch records;
Dissolution data;
Polymer specifications;
Bioequivalence data;
FDA deficiency correspondence;
Expert testing;
Patent prosecution history;
Claim-construction evidence.

A generic applicant may pursue a noninfringement theory based on dissolution, a validity challenge based on prior art, or both. Potential prior-art areas include earlier tranexamic acid controlled-release tablets, hydrophilic matrix technology, cellulose ether systems, and prior pharmacokinetic disclosures.

How strong is the patent estate for tranexamic acid modified-release tablets?

The patent estate appears concentrated rather than diversified. US 7,947,739 provides meaningful formulation coverage, but the patent is vulnerable to design-around strategies because the claims depend on measurable technical parameters.

Strength factor	Assessment
Active-ingredient coverage	Narrow; does not broadly protect tranexamic acid
Dosage-form coverage	Focused on tablets
Polymer coverage	Broad in claims 1 and 11; narrower in HPMC claims
Dose coverage	Strong focus on approximately 650 mg
Dissolution coverage	Important but experimentally variable
PK coverage	Narrower and more difficult to establish
Manufacturing coverage	Limited; no broad process monopoly apparent from the supplied claims
Biosimilar protection	None; tranexamic acid is a small molecule
Design-around potential	Material, particularly through release profile and polymer selection

The most commercially important combination is a 650-mg tablet using HPMC at approximately 15% with a release profile matching the claimed window. A formulation that changes the polymer concentration, alters the release curve, uses a different dosage form, or avoids the claimed dose may reduce literal infringement risk.

What generic launch scenarios exist?

Scenario 1: Immediate-release tranexamic acid

An immediate-release product may avoid the modified-release dissolution claims. It could still compete for tranexamic acid prescriptions, but it may not be therapeutically or regulatorily substitutable for Lysteda.

Scenario 2: Modified-release tablet with a different polymer

A product using a non-cellulose release system may avoid the literal polymer limitations. The doctrine of equivalents could become relevant, but the result would depend on the patent record and the functional similarity of the substitute.

Scenario 3: HPMC product outside the claimed concentration

A product containing less than 10% or more than 35% HPMC may avoid the literal concentration range. The formulation would still need to avoid other claim elements and any equivalents argument.

Scenario 4: HPMC product with a different dissolution profile

A product releasing more than approximately 70% at 45 minutes or failing to reach approximately 100% by 120 minutes may avoid the principal profile claims. Testing must use the specified conditions.

Scenario 5: Product launched after patent expiry

If the patent has expired and no separate enforceable patent or exclusivity period blocks approval, the formulation patent should not prevent launch. Regulatory approval, labeling, substitution status, and any other Orange Book-listed patent remain separate issues.

Does US 7,947,739 cover manufacturing methods?

The supplied claims are product claims. They do not independently claim:

A wet-granulation process;
A direct-compression process;
A particular granulator;
A drying temperature;
A compression force;
A coating process;
A manufacturing facility;
A specific HPMC grade.

Claim 3 narrows the product to a matrix tablet containing pregranulated drug mixed with the modified-release material. That limitation creates process-related evidence, but claim 3 remains a formulation claim. A manufacturer could avoid claim 3 by using a different manufacturing sequence while still potentially infringing claims 1, 11, 16, or 18.

What geographic coverage does the patent provide?

US 7,947,739 provides U.S. rights only. It does not directly block products in Canada, Europe, Japan, China, or other jurisdictions.

International risk must be assessed family by family. Foreign counterparts may have:

Different claim scope;
Different prosecution amendments;
Different expiration dates;
Different validity outcomes;
No granted patent;
Separate supplementary protection or patent-term rules.

A U.S. launch analysis therefore cannot be transferred automatically to other markets. The key geographic question is whether a corresponding national patent remains in force where the product will be manufactured, imported, or sold.

What licensing deals affect the patent?

The patent claims supplied do not establish ownership history, licensing terms, royalty obligations, or settlement provisions. Commercial rights for Lysteda have involved the NDA holder and product commercialization arrangements, but a license covering US 7,947,739 cannot be inferred solely from the claim text.

A diligence review should distinguish:

Patent ownership;
NDA ownership;
U.S. marketing rights;
Manufacturing rights;
Royalty-bearing licenses;
ANDA settlements;
Authorized-generic arrangements.

Patent assignment records are maintained by the USPTO. Settlement terms may appear in FTC filings, court orders, or public company disclosures if the parties were required to report them (Federal Trade Commission, n.d.; U.S. Patent and Trademark Office, n.d.).

Key Takeaways

US 7,947,739 is a formulation patent for modified-release 650-mg tranexamic acid tablets.
Claims 1 and 11 cover multiple cellulose-based release polymers at approximately 10% to 35% by weight.
Claims 16 and 18 focus specifically on HPMC.
Claims 17 and 19 target approximately 15% HPMC.
The dissolution profile is a central infringement limitation and must be tested under the specified USP conditions.
Claims 8 through 10 and 12 through 13 add narrower Cmax and Tmax limitations.
Immediate-release tranexamic acid is not automatically covered by these claims.
Tranexamic acid is a small molecule, so biosimilar competition is irrelevant; the applicable pathway is ANDA approval.
Patent term, Orange Book listing, pediatric extension, and any other listed patent must be verified separately from the claim scope.
The principal design-around routes are changing polymer identity, polymer concentration, release profile, dosage form, or dose.

FAQs

Can a 650-mg tranexamic acid tablet avoid US 7,947,739?

Yes. Avoidance may be possible if the tablet does not contain a claimed cellulose-based polymer, falls outside the claimed polymer concentration, or fails the specified dissolution profile. All claim elements must be evaluated together.

Does using a different HPMC supplier avoid the patent?

No. Supplier identity alone is unlikely to avoid infringement. The relevant issues are whether the material is HPMC, its concentration, and whether the finished tablet meets the claimed performance limitations.

Does claim 3 cover wet granulation itself?

No. Claim 3 covers a tablet containing pregranulated drug mixed with the modified-release material. It is a product limitation, not a standalone manufacturing-process claim.

Can a generic applicant challenge the patent without copying the Lysteda formulation?

Yes. An ANDA applicant may assert noninfringement, invalidity, or both. The applicant can argue that its formulation does not satisfy the polymer, concentration, dose, dissolution, or PK limitations.

Is tranexamic acid subject to biosimilar approval?

No. Tranexamic acid is a chemically synthesized small molecule. A competing product would generally use the ANDA pathway, not the biosimilar pathway under the Public Health Service Act.

References

Food and Drug Administration. (2009). Lysteda (tranexamic acid) tablets: Prescribing information. U.S. Department of Health and Human Services.

Food and Drug Administration. (2024a). Approved drug products with therapeutic equivalence evaluations. U.S. Department of Health and Human Services.

Food and Drug Administration. (2024b). Abbreviated new drug application (ANDA) process. U.S. Department of Health and Human Services.

Federal Trade Commission. (n.d.). Pharmaceutical patent settlements. U.S. Federal Trade Commission.

U.S. Patent and Trademark Office. (n.d.). U.S. Patent No. 7,947,739, Tranexamic acid formulation. U.S. Department of Commerce.

United States Pharmacopeia. (2004). USP 27-NF 22: General chapter 711, dissolution. United States Pharmacopeial Convention.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Japan	2008508275	⤷ Start Trial
Japan	2008508276	⤷ Start Trial
Japan	2011168596	⤷ Start Trial
Japan	2014193878	⤷ Start Trial
Japan	5000504	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 7,947,739

Summary for Patent: 7,947,739