U.S. Patent 3,950,405: Tranexamic Acid Claim Scope, Expiration, and Patent Landscape

U.S. Patent 3,950,405 covers the active pharmaceutical ingredient tranexamic acid, chemically identified as trans-4-(aminomethyl)cyclohexane-1-carboxylic acid. Its single claim is a direct composition-of-matter claim. The patent expired decades ago, so it does not currently block manufacture, sale, importation, formulation, or therapeutic use of tranexamic acid in the United States. Current commercial risk is concentrated in later formulation, dosage-regimen, manufacturing, and method-of-use patents rather than in the 1976 compound patent.

What does U.S. Patent 3,950,405 claim?

The patent contains one substantive claim:

“Trans-4-aminomethylcyclohexane-1-carboxylic acid.”

The claimed compound is tranexamic acid, also known as TXA. Its principal identifiers are:

Attribute	Information
Active ingredient	Tranexamic acid
Chemical name	trans-4-(aminomethyl)cyclohexane-1-carboxylic acid
Molecular formula	C8H15NO2
CAS Registry Number	1197-18-8
Therapeutic class	Antifibrinolytic
U.S. patent	3,950,405
Patent type	Composition of matter
Number of substantive claims	One
Patent issue date	April 13, 1976
Original patent holder or applicant group	Japanese pharmaceutical research interests associated with tranexamic acid development
Current enforceability	Expired

The claim is unusually narrow in wording but commercially broad in effect because it covers the active molecule itself rather than a particular tablet, injection, indication, manufacturing process, or dosage schedule.

How broad is the claim to trans-4-aminomethylcyclohexane-1-carboxylic acid?

The claim covers the trans compound as a chemical entity. A product that contains tranexamic acid as the claimed active ingredient would have fallen within the claim during the patent term, subject to ordinary claim-construction principles.

The claim does not expressly recite:

A pharmaceutical composition;
A specific salt;
A particular dosage form;
An injectable solution;
An oral tablet;
A controlled-release formulation;
A treatment method;
A hemostatic or antifibrinolytic indication;
A manufacturing process;
A purity threshold;
A particle-size limitation;
A combination with another drug; or
A specific dosing regimen.

Does the patent cover tranexamic acid salts?

The literal claim identifies the free acid, trans-4-aminomethylcyclohexane-1-carboxylic acid. It does not expressly claim a salt such as a hydrochloride, sodium salt, or another pharmaceutically acceptable salt.

A salt can raise separate claim-construction and infringement questions because the isolated commercial substance may have a different ionic form from the neutral acid. During the patent term, coverage of a salt would have depended on the patent’s specification, prosecution history, chemical equivalence, and the applicable infringement theory. The patent’s practical relevance is now historical because the patent has expired.

Does the claim cover the cis isomer?

No. The claim expressly requires the trans configuration. The cis isomer is structurally different and is outside the literal scope of the claim.

A product containing both cis and trans material would require a separate analysis. The claim does not specify a purity percentage or define an allowable amount of the cis isomer. A mixture containing the claimed trans compound could have presented infringement issues during the term, depending on the product composition and applicable claim interpretation.

Does the claim cover formulations and finished products?

The patent does not claim a formulation as such. During the patent term, a finished tablet, capsule, or injection containing the claimed compound could have implicated the composition claim because the active ingredient was present in the claimed form. The patent did not need to recite the dosage form to reach the active molecule.

The claim would not, by itself, establish protection for a formulation that contains no tranexamic acid. It also would not protect a later formulation feature, such as extended release, excipient selection, tablet hardness, coating, or dissolution profile, unless that feature was covered by a separate patent.

When did U.S. Patent 3,950,405 expire?

For a patent issued in 1976, the governing pre-Uruguay Round patent term was generally 17 years from the issue date. On that basis, U.S. Patent 3,950,405 expired on or about April 13, 1993, absent an unusual term adjustment, extension, or terminal disclaimer. The public patent record identifies the patent as expired. [1]

Milestone	Date or status
Patent issued	April 13, 1976
Standard term applicable to the patent	17 years from issue
Approximate statutory expiration	April 13, 1993
Current status	Expired
Current blocking effect	None for ordinary U.S. manufacture or sale of tranexamic acid

Patent term extension under 35 U.S.C. § 156 was not available in the modern form for this historical patent in a way that would restore the expired compound right. Patent-term adjustment under current law also does not convert this patent into an enforceable right today.

What products contain the compound covered by U.S. Patent 3,950,405?

Tranexamic acid is marketed in multiple U.S. dosage forms and under multiple product names.

Product or category	Manufacturer or sponsor	Dosage form	FDA status
Cyklokapron	Pfizer	Intravenous injection	FDA-approved antifibrinolytic product
Lysteda	Ferring Pharmaceuticals	Oral tablets	FDA-approved for cyclic heavy menstrual bleeding
Generic tranexamic acid	Multiple manufacturers	Injection and oral tablets	FDA-approved generic products
Hospital-compounded or institutional preparations	Various	Oral or injectable	Subject to applicable FDA and pharmacy rules

The FDA approved Cyklokapron tranexamic acid injection for reduction or prevention of bleeding in selected surgical and dental settings, including use in patients with hemophilia undergoing tooth extraction. [2] FDA approved Lysteda in 2009 for cyclic heavy menstrual bleeding. [3]

The underlying compound patent did not create a continuing exclusivity right for either product. Any present patent exposure must be analyzed against later patents listed for the relevant product, as well as patents covering manufacturing or particular uses.

What is the Orange Book status of tranexamic acid?

The Orange Book is relevant principally to FDA-approved products, not to the expired compound patent itself. U.S. Patent 3,950,405 should not be treated as a current Orange Book barrier.

Orange Book analysis must distinguish among:

The active ingredient;
The reference listed drug;
Product-specific patents;
Method-of-use patents;
Exclusivity codes;
The dosage form and route of administration.

For tranexamic acid, the active ingredient has long been off-patent. Generic approval therefore depends on satisfying the applicable abbreviated new drug application requirements and addressing any still-listed product-specific patents or regulatory exclusivities for the relevant reference product. The existence of a later patent covering Lysteda, Cyklokapron, or a particular regimen would not revive U.S. Patent 3,950,405.

The FDA Orange Book identifies patent information submitted for approved drug products and provides the relevant listing framework. [4] A product-level review should be performed separately for oral tablets and injectable products because their patents, labeling, and regulatory histories can differ.

Are there Paragraph IV challenges involving tranexamic acid?

Paragraph IV risk is product-specific. A generic applicant may certify that a listed patent is invalid, unenforceable, or will not be infringed. That certification can trigger litigation under the Hatch-Waxman Act.

For the expired compound patent, a Paragraph IV challenge is no longer commercially meaningful. The patent cannot support a current infringement action. Any modern Paragraph IV dispute involving tranexamic acid would more likely concern:

A later oral-tablet formulation;
A method of treating heavy menstrual bleeding;
A dosing schedule;
A specific release profile;
A product-specific manufacturing process; or
A patent listed for a particular reference drug.

A generic applicant seeking approval for a basic tranexamic acid product generally faces a different risk profile from an applicant seeking to copy a patented branded formulation or indication. The former can rely on the expired compound patent landscape. The latter may need a Paragraph IV certification, a section viii statement, a carve-out of a patented use, or a non-infringement strategy.

What formulation patents protect tranexamic acid products?

The 3,950,405 patent is not a formulation patent. Later formulation patents may protect commercial attributes such as:

Oral tablet strength;
Modified or extended release;
Dissolution behavior;
Excipient combinations;
Tablet coating;
Stability;
Unit-dose packaging;
Injectable concentration;
Sterility or container-closure configurations; and
Administration schedules tied to a particular formulation.

These later rights are separate from the expired composition claim. Their enforceability depends on their individual filing dates, priority claims, patent terms, prosecution history, claim scope, and Orange Book listing status.

A formulation patent generally cannot prevent all manufacture of tranexamic acid. It can restrict copying of the claimed formulation or process. A competitor may avoid infringement by using a different excipient system, release mechanism, dosage form, concentration, or manufacturing route, provided the alternative does not fall within the patent claims.

What method-of-use patents affect tranexamic acid?

Tranexamic acid has applications across several bleeding-related settings, including:

Cyclic heavy menstrual bleeding;
Dental extraction in patients with hemophilia;
Trauma-related hemorrhage;
Perioperative bleeding;
Postpartum hemorrhage;
Epistaxis;
Oral and maxillofacial surgery; and
Certain dermatologic or cosmetic uses.

The historic compound patent does not claim any of these uses. A later method patent may claim a particular patient population, dose, timing, route, treatment duration, or combination therapy.

Method-of-use protection is narrower than compound protection. A generic applicant may be able to market the same active ingredient for unpatented indications while carving out a patented use from its label, subject to FDA requirements and induced-infringement considerations.

What manufacturing and intellectual-property barriers remain?

The expired composition patent removes the primary molecule-level barrier. Commercial barriers may still arise from manufacturing know-how and regulatory requirements.

Manufacturing considerations

Tranexamic acid production may involve control of:

Trans/cis isomer ratio;
Chemical purity;
Residual solvents;
Residual starting materials;
Crystallization conditions;
Particle size;
Polymorphic or solid-state properties;
Sterile manufacturing for injection;
Stability in aqueous solution; and
Analytical methods.

These attributes may be protected by later process or formulation patents, trade secrets, or quality-control know-how. Trade-secret protection does not prevent independent development of the same process, but it can increase the time and cost required to qualify a supplier.

Regulatory considerations

An ANDA applicant must establish pharmaceutical equivalence and bioequivalence where required, comply with current good manufacturing practices, and address the reference product’s labeling. Injectable products carry additional requirements involving sterility, particulate matter, container closure, and manufacturing controls.

The expired 3,950,405 patent does not remove these FDA obligations.

How strong is the patent estate for tranexamic acid?

The estate is weak at the active-ingredient level and potentially differentiated at the product level.

Patent layer	Status	Commercial significance
Basic tranexamic acid compound	Expired	No current exclusionary value
Cis/trans stereochemical distinction	Historical scope only under 3,950,405	No current blocking right from this patent
Conventional oral tranexamic acid	Generally mature generic market	Low molecule-level risk
Injectable tranexamic acid	Mature product category	Manufacturing and regulatory execution remain important
Branded oral formulation	Potential later patent exposure	Product-specific review required
Heavy menstrual bleeding method	Potential later method claims	Relevant to label strategy and Paragraph IV analysis
Trauma or surgical use	Mostly clinical-use and regulatory issues	Patent exposure depends on specific later claims
Manufacturing process	May include later patents or trade secrets	Supplier and CMC diligence required

The commercial value of the old patent was concentrated in its composition-of-matter coverage. Once it expired, competitive advantage shifted to regulatory approvals, supply reliability, formulation differentiation, branding, hospital contracts, and later product-specific intellectual property.

What generic launch risks exist for tranexamic acid?

A conventional generic launch faces substantially lower patent risk than a copy of a branded, patented formulation.

Low-risk scenario

A manufacturer launches a standard immediate-release oral tablet or conventional injection after confirming that:

The active ingredient patent is expired;
No blocking product patent remains listed for the relevant reference product;
The proposed label excludes patented indications where necessary;
The formulation does not copy protected release or excipient features; and
FDA requirements are satisfied.

Moderate-risk scenario

Risk increases where the applicant seeks to copy:

A branded tablet technology;
A specific dosing regimen;
A patented use for heavy menstrual bleeding;
A controlled-release profile; or
A product-specific manufacturing process.

High-risk scenario

The highest exposure arises when the applicant:

Uses the branded product’s patented formulation without a design-around;
Includes a patented indication in the proposed label;
Relies on a Paragraph IV certification against a commercially significant later patent;
Launches before litigation resolution; or
Depends on a single supplier with a potentially protected process.

Which companies compete in tranexamic acid?

The U.S. competitive landscape includes originator-sponsored products, generic manufacturers, hospital suppliers, and contract manufacturers.

Key commercial participants include:

Pfizer, through Cyklokapron injection;
Ferring Pharmaceuticals, through Lysteda tablets;
Generic manufacturers supplying tranexamic acid injection and tablets;
Contract manufacturers and active pharmaceutical ingredient suppliers.

Competition is based less on molecule ownership than on:

FDA approval status;
Product availability;
Injectable manufacturing capacity;
Hospital purchasing contracts;
Tablet supply;
API cost;
Quality history;
Label breadth; and
Ability to avoid or resolve later patents.

What is the revenue exposure from U.S. Patent 3,950,405?

There is no current revenue exposure attributable to the expired patent itself. The patent no longer supports an injunction, damages claim, or exclusion from the U.S. market.

Revenue exposure may still arise from later rights connected to branded products. The relevant commercial questions are:

Which reference product is being copied?
Which patents are listed for that product?
Does the proposed label include each patented indication?
Does the formulation practice the claims?
Is a Paragraph IV challenge required?
Is a 30-month stay possible?
Can the applicant launch with a carve-out or design-around?

For tranexamic acid, the basic generic opportunity is structurally more attractive than a protected small-molecule launch because the principal compound patent expired in 1993 and the ingredient has an established regulatory history.

Key Takeaways

U.S. Patent 3,950,405 claims tranexamic acid itself: trans-4-(aminomethyl)cyclohexane-1-carboxylic acid.
The patent contains a single composition-of-matter claim.
It does not expressly claim a formulation, method of use, dosage regimen, or manufacturing process.
The patent issued on April 13, 1976 and expired approximately 17 years later, on April 13, 1993.
It has no current blocking effect on U.S. manufacture, sale, importation, or use of tranexamic acid.
Current patent risk must be assessed against later product, formulation, method-of-use, and process patents.
Paragraph IV analysis is relevant only to later listed patents, not to U.S. Patent 3,950,405.
FDA approval and Orange Book analysis remain product-specific for Cyklokapron, Lysteda, and generic tranexamic acid products.
Generic launch risk is principally regulatory, manufacturing, supply-chain, and later-patent risk rather than basic compound-patent risk.

Frequently Asked Questions

Is U.S. Patent 3,950,405 still enforceable?

No. The patent expired approximately in April 1993 under the 17-year term applicable to the patent.

Does U.S. Patent 3,950,405 cover tranexamic acid tablets?

It claims the active compound, not a tablet formulation. During its term, a tablet containing the claimed compound could have implicated the composition claim. The patent has no current enforceability.

Does the patent cover tranexamic acid injection?

The active compound claim could have reached the compound in an injectable product during the patent term. It did not independently claim sterility, concentration, container closure, or injectable formulation technology.

Can a generic manufacturer sell tranexamic acid in the United States?

The expired compound patent does not prevent sale. The manufacturer must still satisfy FDA approval, labeling, manufacturing, bioequivalence, quality, and any later product-patent requirements.

Does the patent cover use of tranexamic acid for heavy menstrual bleeding?

No. The claim is to the compound and does not recite heavy menstrual bleeding or any other therapeutic indication. Later method-of-use patents must be analyzed separately.

References

U.S. Patent and Trademark Office. (1976). U.S. Patent No. 3,950,405, trans-4-aminomethylcyclohexane-1-carboxylic acid.
U.S. Food and Drug Administration. (2019). Cyklokapron (tranexamic acid) injection prescribing information. Pfizer Laboratories.
U.S. Food and Drug Administration. (2019). Lysteda (tranexamic acid) tablets prescribing information. Ferring Pharmaceuticals.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book. U.S. Department of Health and Human Services.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
	46-69632	Dec 24, 1971

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Belgium	657492	⤷ Start Trial
Brazil	6465652	⤷ Start Trial
Switzerland	444146	⤷ Start Trial
Germany	1443755	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 3,950,405

Summary for Patent: 3,950,405