US Drug Patent 4,254,114: Claim Scope, Expiration, FDA Status, and Amoebiasis Patent Landscape

US Patent 4,254,114 covers a broad method of treating amoebiasis with geminal diphosphonates, commonly called bisphosphonates, at a dosage of approximately 0.1 to 5 mg/kg/day. Claim 1 is a genus claim covering a wide range of substituted diphosphonic acids, salts, and mixtures. Claim 2 narrows that genus to nine listed compounds and their pharmaceutically acceptable salts.

The patent issued in 1981 and is expired. Its claims no longer create a U.S. patent barrier to generic manufacture, clinical use, licensing, or commercialization. No current Orange Book exclusivity or enforceable patent protection appears to arise from US 4,254,114.

What does US Patent 4,254,114 protect?

The patent protects a therapeutic use rather than a particular commercial product, formulation, manufacturing process, or dosing regimen for one named active ingredient.

The core claim elements are:

Claim element	Scope
Disease	Amoebiasis
Patient	Human or “lower animal”
Administration	Administration of the covered compound
Dose	About 0.1 to about 5 mg/kg body weight/day
Chemical class	Geminal diphosphonate compounds
Substitution	Broad R1 and R2 Markush definitions
Chemical chain length	n equals an integer from 1 to about 10
Form	Free acid, pharmaceutically acceptable salts, or mixtures
Claim type	Method of treatment

The patent does not claim every antiamoebic compound. It claims the use of compounds satisfying the structural limitations in the formula and substituent definitions.

Because the formula is supplied in the patent as a drawing, the precise atom-to-atom relationship in the claimed scaffold must be read from the issued patent. The text establishes that the invention concerns geminal diphosphonates, but the complete structural scope depends on the omitted chemical diagram.

How broad is claim 1 of US 4,254,114?

Claim 1 is broad because it combines a large Markush genus with a therapeutic-use limitation.

Chemical scope

The claim allows:

A carbon chain or related structure in which n ranges from 1 to approximately 10.
R1 substituents including hydrogen, C1-C20 alkyl, C2-C20 alkenyl, phenyl, naphthyl, phenylethenyl, benzyl, halogen, amino, dimethylamino, diethylamino, N-hydroxy-N-ethylamino, acetylamino, carboxymethyl, phosphonomethyl, hydroxyphosphonomethyl, and polyphosphonomethyl groups.
R2 substituents including hydrogen, methyl, ethyl, propyl, butyl, amino, benzyl, halogen, hydroxyl, carboxymethyl, phosphonomethyl, and phosphonoethyl groups.
Pharmaceutically acceptable salts.
Mixtures of covered compounds.

The R1 list is particularly expansive. It reaches simple hydrocarbons, aromatic groups, halogens, amino substituents, and additional phosphonate-containing substituents. The claim therefore attempts to cover a chemical platform rather than a single active pharmaceutical ingredient.

Therapeutic scope

The therapeutic limitation is equally important. A compound falls within claim 1 only when it is administered for treating amoebiasis at the claimed daily dose range.

A compound that satisfies the chemical formula but is used only for osteoporosis, Paget’s disease, hypercalcemia, or another non-amoebiasis indication would not, by that use alone, practice the claimed method. Conversely, administration for amoebiasis at a materially different dose could raise questions concerning literal infringement and the interpretation of “about.”

Dose limitation

The range extends from approximately 0.1 to 5 mg/kg/day. The word “about” creates a potential boundary issue, but it does not eliminate the dose limitation.

The claim does not specify:

A single daily dose versus divided doses.
Oral, parenteral, rectal, or other administration.
Duration of treatment.
Tissue amoebiasis versus intestinal amoebiasis.
Confirmed infection versus prophylactic treatment.
Combination therapy with a second anti-infective.

Those omissions make the claim broad in treatment format but narrower than a claim covering all uses of the compounds against amoebiasis.

What compounds are listed in claim 2?

Claim 2 identifies nine species or compound classes:

Compound identified in claim 2	Scope category
Ethane-1-hydroxy-1,1-diphosphonic acid	Hydroxy-substituted diphosphonate
Dichloromethane diphosphonic acid	Halogenated diphosphonate
Methane hydroxy diphosphonic acid	Hydroxy diphosphonate
Nonane-1,1-diphosphonic acid	Long-chain diphosphonate
Aminomethane diphosphonic acid	Amino-substituted diphosphonate
Ethane-1-amino-1,1-diphosphonic acid	Amino-substituted ethane derivative
Methane diphosphonic acid	Unsubstituted diphosphonate
Nonane-1-hydroxy-1,1-diphosphonic acid	Long-chain hydroxy diphosphonate
Propane-3-amino-1,1-diphosphonic acid	Amino-substituted propane derivative

Claim 2 also covers pharmaceutically acceptable salts and mixtures of the listed compounds.

Claim 2 is narrower than claim 1 because it selects named members from the broader Markush class. It may be easier to practice and enforce against a specific product, but it remains subject to the same treatment, patient, and dosage limitations in claim 1.

How does claim 2 compare with claim 1?

Claim 2 depends on claim 1. A defendant must satisfy both the general requirements of claim 1 and the specific compound selection in claim 2.

Issue	Claim 1	Claim 2
Chemical breadth	Very broad genus	Defined species and species groups
Dose	0.1-5 mg/kg/day, approximately	Same
Disease	Amoebiasis	Same
Salts	Included	Included
Mixtures	Included	Included
Enforcement target	Any covered compound in the genus	One of the listed compounds
Vulnerability	Potential written-description, enablement, or definiteness issues	Narrower scope but dependent on claim 1

The narrower claim could have provided a fallback position during prosecution or litigation. That protection has no current blocking effect because the patent term has ended.

When did US Patent 4,254,114 expire?

US Patent 4,254,114 issued on March 3, 1981. For a U.S. patent governed by the pre-Uruguay Round Agreement Act term, the ordinary term was 17 years from issuance. On that basis, the patent expired on March 3, 1998, absent an unusual term adjustment, terminal disclaimer, or other extension.

The patent is therefore more than 25 years past its expected expiration date. The claims cannot support a current U.S. patent-infringement action.

Event	Date or status
Patent issued	March 3, 1981
Ordinary statutory term	17 years from issuance
Expected expiration	March 3, 1998
Current status	Expired
Patent-term restoration	No apparent relevance
Pediatric exclusivity	Not applicable
Current enforceability	None

The governing statutory framework for older patents differs from the 20-year-from-earliest-effective-filing-date system used for later U.S. applications. The term here is evaluated under the issuance-based regime applicable to the patent’s vintage. (35 U.S.C. § 154).

What is the Orange Book status of US Patent 4,254,114?

US Patent 4,254,114 should not be treated as a current Orange Book barrier.

The Orange Book lists patents submitted by sponsors in connection with approved drug products. A historical method-of-use patent can be relevant to an approved product only if the sponsor submitted it and the listing remains legally and administratively relevant. An expired patent does not provide current market exclusivity.

The patent also appears unrelated to a currently approved U.S. bisphosphonate product labeled for amoebiasis. Bisphosphonates such as etidronate, alendronate, pamidronate, and zoledronic acid are associated primarily with bone and mineral disorders, not FDA-approved amoebiasis treatment.

Orange Book issue	Assessment
Current patent protection from US 4,254,114	None
Current use code	No current blocking use code apparent
Approved amoebiasis product based on patent	No apparent product
Generic approval barrier	None from this patent
Relevant regulatory pathway	NDA or ANDA, depending on the proposed product

An applicant seeking approval for a modern antiamoebic product would face current FDA requirements for safety, efficacy, chemistry, manufacturing, and labeling. It would not face an unexpired patent claim from US 4,254,114.

What FDA regulatory status applies to the claimed amoebiasis use?

The patent does not establish FDA approval. Patentability and regulatory approval are separate questions.

Current antiamoebic treatment commonly relies on agents such as metronidazole or tinidazole for invasive disease, followed by a luminal agent when clinically indicated. Paromomycin, iodoquinol, and diloxanide-related therapies have been used for intestinal eradication. CDC treatment guidance does not identify geminal diphosphonates as standard U.S. therapy for amoebiasis. (Centers for Disease Control and Prevention, n.d.).

A sponsor attempting to commercialize a diphosphonate for amoebiasis would need to establish:

Adequate antiamoebic efficacy.
Human safety at the proposed dose.
Appropriate gastrointestinal and systemic exposure.
Renal and mineral-metabolism safety.
Product quality and manufacturing controls.
A compliant label for the claimed indication.

The patent’s dose range does not constitute a validated clinical dose. It is a claim limitation.

Does the patent create Paragraph IV risk?

No current Paragraph IV risk arises from US 4,254,114 because the patent is expired.

A Paragraph IV certification applies when an ANDA applicant asserts that a listed patent is invalid, unenforceable, or will not be infringed. An expired patent cannot ordinarily delay approval as a current patent obstacle. The principal Hatch-Waxman risks would instead involve:

Current patents covering a particular formulation.
New crystalline or salt forms.
Combination products.
Drug-delivery systems.
Manufacturing processes.
New method-of-use claims.
Regulatory exclusivity attached to a later-approved product.

If no relevant unexpired patent is listed for the reference product, an ANDA applicant would not need to challenge US 4,254,114.

Are biosimilar issues relevant to this patent?

Biosimilar risk is not relevant.

The claimed compounds are chemically synthesized small molecules, not biologics. The applicable competitive pathways would be generic-drug pathways under section 505(j), a suitability petition in limited circumstances, or a full NDA under section 505(b)(1) or 505(b)(2), depending on the product and the available reference data.

A bisphosphonate product would not use the 351(k) biosimilar pathway. (U.S. Food and Drug Administration, n.d.-a).

What formulation patents are covered by US 4,254,114?

None are expressly claimed.

The patent claims a method of treating amoebiasis with chemical compounds. It does not, based on the supplied claims, claim:

Tablets.
Capsules.
Injectable solutions.
Suspensions.
Coated dosage forms.
Controlled-release systems.
Nanoparticles.
Liposomes.
Specific excipients.
Particle-size distributions.
A defined pH or dissolution profile.
A manufacturing process.

A later patent could theoretically claim a formulation containing one of the covered diphosphonates. Such a later patent would need to be analyzed separately. It would not revive or extend US 4,254,114.

What manufacturing and intellectual-property barriers remain?

The expired patent removes one historical use barrier but does not eliminate technical or regulatory barriers.

Manufacturing considerations

Geminal diphosphonates can present manufacturing and quality-control issues involving:

Control of phosphorus-containing impurities.
Isomeric or substitutional byproducts.
Acidic or highly polar intermediates.
Salt selection.
Residual metals and solvents.
Assay and impurity methods.
Stability in aqueous formulations.
Compatibility with packaging materials.

A later process patent could protect a more efficient synthesis or a specific impurity profile. A process patent would be independent of the expired therapeutic-use patent.

Regulatory considerations

Bisphosphonate pharmacology raises questions about:

Renal clearance.
Hypocalcemia and mineral disturbances.
Gastrointestinal tolerability.
Dose-dependent tissue exposure.
Long-term skeletal retention for certain compounds.
Interactions with calcium and polyvalent cations.
Suitability for pediatric or pregnant populations.

These factors could materially affect commercial viability even where patent freedom to operate is clear.

Which companies are challenging US Patent 4,254,114?

No current challenger is expected because the patent expired in 1998. Paragraph IV litigation, ANDA litigation, or a settlement agreement directed specifically to this patent would have no present commercial significance.

The original patent holder was associated with the Procter & Gamble research and patent portfolio in the bisphosphonate field. Current commercial competition in amoebiasis is centered on established anti-infective manufacturers and suppliers of metronidazole, tinidazole, luminal agents, and combination treatment, rather than on enforcement of this patent.

The absence of current litigation should not be confused with proof that no historical dispute ever existed. A complete litigation history would require docket-level review of PACER, USPTO records, and reported decisions. The patent’s expiration means any historical dispute has no continuing exclusionary effect.

How strong is the patent estate for the claimed amoebiasis use?

The historical claim estate was broad in chemical coverage but narrow in commercial relevance.

Strength factor	Assessment
Genus breadth	Broad
Specific compound fallback	Present through claim 2
Disease limitation	Narrower than a composition claim
Dose limitation	Creates design-around and proof issues
Formulation protection	Not apparent
Manufacturing protection	Not apparent
Regulatory exclusivity	Not created by the patent
Current enforceability	None
Commercial blocking value	Zero in the United States

The principal legal vulnerabilities would historically have included written description and enablement across a large Markush genus, definiteness of “about,” the meaning of “lower animal,” support for the full compound list, and proof that each covered compound treats amoebiasis at the claimed dose. Those issues are now academic for U.S. enforcement because the patent has expired.

How does this patent compare with modern antiamoebic competition?

US 4,254,114 covers a chemically unusual treatment concept rather than the established antiamoebic market.

Therapy class	Typical role	Relationship to US 4,254,114
Nitroimidazoles	Invasive amoebiasis treatment	Competing therapy, not covered
Luminal agents	Eradication of intestinal infection	Competing therapy, not covered
Aminoglycosides such as paromomycin	Luminal treatment	Competing therapy, not covered
Bisphosphonates	Bone and mineral disorders	Chemical class targeted by the patent
New formulations	Potential delivery improvements	Could be subject to later patents
Combination products	Broader treatment regimens	Not expressly claimed

The patent could have been commercially important only if one of the claimed compounds had advanced through clinical development and regulatory approval for amoebiasis. The absence of such a recognized product limits the patent’s historical commercial impact.

What generic launch scenarios exist today?

A current sponsor could pursue several routes:

Develop a diphosphonate product for amoebiasis under a full NDA.
Use a 505(b)(2) application if an appropriate reference product and bridging data exist.
Pursue an ANDA only if an approved reference product has the required dosage form, active ingredient, route, strength, and therapeutic equivalence pathway.
Develop a formulation or combination product and assess later-filed patents.
License historical know-how only for technical or regulatory value, not for exclusion from competitors.

US 4,254,114 would not delay any of these routes. The meaningful IP analysis would focus on later patents, trade secrets, regulatory exclusivity, and the availability of clinical and manufacturing data.

What geographic coverage remains?

The patent provided protection only in the United States. Its expiration eliminates U.S. exclusivity, but foreign counterparts, if any, would have had separate terms and separate legal status.

Patent rights in Europe, Japan, Canada, and other jurisdictions cannot be inferred from the U.S. patent number. Any foreign family member would require individual review of:

Priority date.
Filing and grant dates.
National-phase status.
Patent-term adjustments.
Supplementary protection certificates.
Lapse or renewal status.
Local claim amendments.

No current U.S. freedom-to-operate restriction should be attributed to foreign family members.

Key Takeaways

US Patent 4,254,114 claims treatment of amoebiasis with a broad genus of geminal diphosphonates.
Claim 1 covers humans and animals, approximately 0.1-5 mg/kg/day, salts, and mixtures.
Claim 2 narrows the invention to nine listed diphosphonate compounds or compound classes.
The patent issued March 3, 1981, and ordinarily expired March 3, 1998.
The patent does not claim a specific formulation, manufacturing process, or composition.
It creates no current Paragraph IV, Orange Book, or U.S. patent-enforcement risk.
Biosimilar analysis is irrelevant because the claimed products are small-molecule chemicals.
Current commercial risk would arise from later formulation, process, combination, or method-of-use patents, not from US 4,254,114.
FDA approval for amoebiasis would require independent clinical, regulatory, and manufacturing support.

FAQs

Can a company commercialize a diphosphonate for amoebiasis without licensing US 4,254,114?

Yes. The patent’s term has expired, so a U.S. license is not required to practice its claims.

Does the patent cover metronidazole or tinidazole?

No. Those nitroimidazole drugs do not fall within the claimed geminal diphosphonate chemical class.

Does claim 1 cover every bisphosphonate drug?

No. Coverage depends on the precise formula, the R1 and R2 substituents, the n value, the amoebiasis indication, and the claimed dose.

Could a later patent block a product that practices US 4,254,114?

Yes. A later patent could cover a formulation, salt, combination, manufacturing process, delivery system, or new therapeutic regimen even though the original use patent is expired.

Is a patent license still useful after US 4,254,114 expires?

It could have technical or historical value if it includes know-how, data, or rights under other unexpired patents. It provides no continuing exclusionary right under the expired U.S. claims.

References

Centers for Disease Control and Prevention. (n.d.). Clinical care of amebiasis. https://www.cdc.gov/amebiasis/hcp/clinical-care/index.html
Google Patents. (n.d.). US4254114A: Treatment of amoebiasis with diphosphonates. https://patents.google.com/patent/US4254114A/en
U.S. Food and Drug Administration. (n.d.-a). Biosimilar and interchangeable biologic products. https://www.fda.gov/drugs/therapeutic-biologics-applications-bla/biosimilar-biological-products
U.S. Food and Drug Administration. (n.d.-b). Approved drug products with therapeutic equivalence evaluations. https://www.fda.gov/drugs/drug-approvals-and-databases/orange-book-data-files
United States Code. (2024). 35 U.S.C. § 154: Contents and term of patent; provisional rights. https://www.law.cornell.edu/uscode/text/35/154

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Belgium	880963	⤷ Start Trial
Japan	H0128006	⤷ Start Trial
Japan	S55120515	⤷ Start Trial
Philippines	14930	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 4,254,114

Summary for Patent: 4,254,114