United States Patent 4,158,055: Amcinonide Scope, Claim Construction, Expiration, and Generic-Entry Risk

United States Patent 4,158,055 covers topical administration of amcinonide, a fluorinated corticosteroid, for treating inflammation in mammals. Its claims are method-of-treatment claims, not claims to amcinonide itself, a finished pharmaceutical composition, a manufacturing process, or a specific commercial product. The patent issued in 1979 and its ordinary 17-year patent term expired in 1996. It therefore presents no current U.S. patent barrier to generic amcinonide products.[1][2]

What drug does U.S. Patent 4,158,055 protect?

The claimed steroid is amcinonide, chemically identified as:

16α,17α-cyclopentylidenedioxy-9α-fluoro-11β,21-dihydroxy-1,4-pregnadiene-3,20-dione 21-acetate.

Amcinonide is a topical glucocorticoid used for inflammatory and pruritic corticosteroid-responsive dermatoses. Commercial topical strengths have included approximately 0.1% cream, ointment, and lotion formulations.[3]

Attribute	Patent and drug relevance
Active ingredient	Amcinonide
Therapeutic class	Topical corticosteroid
Chemical type	Fluorinated pregnadiene steroid with cyclopentylidene acetal
Administration route	Topical
Claimed target	Inflammation in a mammal
Claimed dosage forms	Cream, ointment, foam, ophthalmic ointment, lotion
Claimed concentration range	About 0.01% to about 0.50% in claim 7
Patent type	Method of treatment
U.S. patent status	Expired
Current generic-entry barrier	None from Patent 4,158,055

The patent claims do not use the generic name “amcinonide,” but the structural name in the claims corresponds to that active ingredient.

What is the scope of claim 1?

Claim 1 requires four principal elements:

A method of ameliorating inflammation.
In a mammal.
By topical administration.
Of an anti-inflammatory effective amount of amcinonide in a topical pharmaceutically acceptable carrier.

The claim is broad as to:

The inflammatory condition.
The mammalian species.
The topical body site.
The precise dosage.
The specific carrier.
The commercial dosage form.
The treatment duration and frequency.

The claim is limited by the requirement that amcinonide be administered topically in association with a topical pharmaceutically acceptable carrier. Oral, injectable, implantable, or purely systemic administration would fall outside the express scope of claim 1.

The phrase “anti-inflammatory effective amount” is functional. It does not set a numerical dose. In an infringement analysis, the relevant question would be whether the administered amount is intended and capable of producing an anti-inflammatory effect under the claimed treatment conditions.

The phrase “inflammation in a mammal” gives the claim substantial disease breadth. It is not limited to eczema, psoriasis, dermatitis, or any other named indication. The claim could encompass treatment of a broad range of mammalian inflammatory conditions, provided the administration is topical and the formulation contains the claimed steroid.

How do claims 2 through 6 narrow the patent scope?

Claims 2 through 6 depend on claim 1 and specify particular dosage forms.

Claim	Additional limitation	Practical scope
2	Topical cream	Amcinonide cream treatment
3	Topical ointment	Amcinonide ointment treatment
4	Topical foam	Amcinonide foam treatment
5	Ophthalmic ointment	Topical ocular ointment treatment
6	Topical lotion	Amcinonide lotion treatment

These dependent claims do not claim the cream, ointment, foam, ophthalmic ointment, or lotion as compositions. They claim methods using those dosage forms.

That distinction matters. A product claim would typically identify the ingredients, concentrations, excipients, physical properties, or delivery system of the composition. Claims 2 through 6 instead require use of the dosage form in treating inflammation.

A manufacturer selling an amcinonide cream would not necessarily infringe claims 1 or 2 merely by selling the product. Because the claims are treatment claims, infringement generally requires administration or inducement of the claimed administration. A label that directs topical use for inflammatory conditions could be relevant to induced-infringement analysis under 35 U.S.C. § 271(b), but the expired status of this patent eliminates present enforcement risk.[2]

What does claim 7 protect?

Claim 7 is an independent method claim requiring:

Topical treatment of inflammation in a mammal.
Amcinonide.
A topical pharmaceutically acceptable carrier.
A concentration of about 0.01% to about 0.50%.

Claim 7 is narrower than claim 1 because it adds a concentration limitation. The word “about” creates a potential boundary issue. It would ordinarily be interpreted in the context of the patent specification, formulation technology, measurement precision, and technical understanding of the skilled person.

The claimed range covers the concentrations commonly associated with commercial topical amcinonide products, including 0.1%. It also reaches substantially lower and higher concentrations:

Concentration	Within literal range of claim 7?
0.005%	Generally outside
0.01%	At lower boundary
0.025%	Within
0.05%	Within
0.1%	Within
0.25%	Within
0.5%	At upper boundary
1.0%	Generally outside

Claim 7 does not restrict the dosage form to cream, ointment, lotion, foam, or ophthalmic ointment. Any topical pharmaceutically acceptable carrier could potentially satisfy the claim if the amcinonide concentration falls within the stated range.

Claims 1 and 7 overlap. A topical amcinonide product at 0.1% would fall within the broad treatment concept of claim 1 and the concentration-limited scope of claim 7.

Does Patent 4,158,055 claim the amcinonide molecule itself?

No. The claims provided do not claim:

Amcinonide as a chemical compound.
A pharmaceutical composition containing amcinonide.
A specific cream base.
A particular preservative, solvent, surfactant, or emulsifier.
A manufacturing process.
A crystalline form or polymorph.
A salt or solvate.
A container, applicator, metered-dose system, or package.
A specific inflammatory disease.

The patent uses the chemical identity of amcinonide as an element of the treatment method. It does not create product-by-itself protection for the active ingredient.

This distinction limits the patent’s commercial reach even before expiration. A competitor’s formulation could differ materially in vehicle, excipients, manufacturing process, packaging, or particle characteristics while still potentially falling within the method claims if its product were used as claimed.

When did U.S. Patent 4,158,055 lose exclusivity?

Patent 4,158,055 issued in 1979. Under the pre-Uruguay Round patent-term regime applicable to patents of that period, the ordinary term was 17 years from issuance. The patent therefore expired in 1996, assuming no unusual terminal-disclaimer or term-adjustment issue affecting the calculation.[1][2]

Event	Timing
Patent issuance	1979
Ordinary statutory term	17 years from issuance
Expiration	1996
Current enforceability	Expired
Current Orange Book patent barrier	None attributable to this patent

Patent expiration eliminates the right to exclude others from practicing the claimed methods. It also removes the relevance of the patent to a present Paragraph IV certification.

What is the Orange Book status of amcinonide?

Patent 4,158,055 should not be treated as a current Orange Book patent barrier because it expired decades ago. The Orange Book identifies approved drug products and, where applicable, patents and exclusivities associated with listed reference products.[4]

For a generic amcinonide applicant, the regulatory analysis would focus on:

The applicable reference listed drug.
Product-specific FDA approval status.
Dosage form and strength.
Abbreviated New Drug Application requirements.
Therapeutic equivalence.
Topical product quality and sameness.
Any currently listed patents associated with the reference product.

An expired 1979 method patent does not block ANDA approval or commercial launch. The relevant FDA pathway for a conventional generic topical product would generally be an ANDA under section 505(j) of the Federal Food, Drug, and Cosmetic Act, subject to the product’s regulatory classification and any product-specific requirements.[4][5]

Are there Paragraph IV challenges to Patent 4,158,055?

A Paragraph IV certification is not commercially meaningful for this patent because the patent has expired. Paragraph IV is designed to challenge a listed patent that the applicant asserts is invalid, unenforceable, or not infringed. An expired patent cannot ordinarily support a continuing patent-based delay to generic approval.[6]

The practical outcome is:

Issue	Assessment
Paragraph IV relevance	None for the expired patent
30-month stay risk	None based on this patent
Patent certification impact	No current launch block
Generic launch timing	Driven principally by FDA approval and commercial readiness
Litigation exposure	No continuing enforcement risk from Patent 4,158,055

Historical Paragraph IV activity cannot be inferred from the claims alone. The patent’s expiration makes any historical challenge immaterial to current U.S. entry.

What formulation patents protect amcinonide products?

The supplied claims do not contain formulation-patent protection. Claims 2 through 6 identify dosage forms but do not claim their formulation architecture.

There is no claim-level protection here for:

An emulsion system.
A water-in-oil or oil-in-water cream.
A hydrocarbon ointment base.
A hydroalcoholic lotion.
A propellant-based foam.
A specific ophthalmic vehicle.
A preservative system.
A penetration-enhancing system.
A rheology modifier.
A particle-size distribution.
A particular pH or viscosity range.

A later patent could theoretically have protected one of those features, but such protection would have to arise from a separate patent family. Patent 4,158,055 does not establish those rights.

Is there biosimilar risk for amcinonide?

No. Amcinonide is a chemically synthesized small-molecule corticosteroid, not a biologic. Biosimilar regulation under the Public Health Service Act is therefore not the relevant pathway.

Competitive products would be conventional generics or other topical corticosteroid products. The regulatory and commercial issues are pharmaceutical equivalence, topical product performance, manufacturing quality, and therapeutic equivalence rather than biosimilarity.[5]

What generic-entry risks remain after patent expiration?

The principal remaining risks are regulatory and commercial, not patent-based.

Regulatory risks

Topical dermatological products can present product-specific challenges involving:

Active-ingredient identity and assay.
Uniformity of drug distribution.
Microbial quality.
Preservative effectiveness.
Physical stability.
In vitro release.
In vitro permeation.
Vehicle sameness or acceptable difference.
Comparative clinical performance where required.

FDA has developed product-specific approaches for topical dermatological products, including in vitro release testing and related pharmaceutical-quality assessments.[5]

Manufacturing risks

Manufacturing know-how may remain commercially valuable even without enforceable patent protection. Relevant barriers may include:

Reproducible dispersion of amcinonide.
Control of viscosity and rheology.
Homogeneity across batches.
Stability in the selected vehicle.
Filling and packaging performance.
Compatibility with tubes, pumps, or foam containers.
Scale-up from laboratory to commercial production.

These are trade-secret, quality-system, and execution risks. They are not rights created by Patent 4,158,055.

Commercial risks

Amcinonide competes with other topical corticosteroids, including products containing fluocinolone acetonide, triamcinolone acetonide, hydrocortisone, desonide, betamethasone, and clobetasol. Prescriber selection depends on potency, disease site, formulation, price, payer coverage, and generic availability.

The patent creates no continuing revenue protection for the original sponsor. Any present revenue exposure would depend on brand retention, generic substitution, channel position, manufacturing cost, and market share.

How strong is the patent estate for amcinonide?

The patent estate represented by Patent 4,158,055 is weak as a current commercial asset because the patent is expired and its claims are limited to treatment methods.

Patent-estate category	Status based on Patent 4,158,055
Composition-of-matter protection	Not claimed in the supplied claims
Topical treatment method	Claimed, but expired
Concentration protection	Claimed at 0.01%-0.50%, but expired
Dosage-form protection	Limited method claims, expired
Formulation protection	Not claimed
Manufacturing protection	Not claimed
Device protection	Not claimed
Biologic exclusivity	Not applicable
Current U.S. blocking right	None

The patent had potentially broad historical scope against topical therapeutic use of amcinonide. It did not provide a durable, layered estate covering formulation technology, manufacturing, delivery systems, or post-expiration lifecycle products.

What licensing deals or litigation affect this patent?

The claims alone do not establish an assignment, license, settlement, or litigation history. Patent ownership and licensing rights must be distinguished from claim scope. A patent may have changed hands or been licensed without those transactions appearing in the claim language.

The patent’s expiration also means that any historical license or litigation involving the patent would have no continuing exclusionary effect unless separate contractual obligations survived independently. No current litigation risk follows from the expired claims.

Key Takeaways

Patent 4,158,055 covers topical treatment of mammalian inflammation with amcinonide.
Claim 1 is a broad method claim requiring topical administration in a pharmaceutically acceptable carrier.
Claims 2 through 6 narrow the method by dosage form: cream, ointment, foam, ophthalmic ointment, or lotion.
Claim 7 covers topical amcinonide concentrations of about 0.01% to about 0.50%.
The patent does not claim amcinonide as a compound, a specific formulation, or a manufacturing process.
The patent issued in 1979 and expired in 1996 under the ordinary pre-URAA term.
It creates no current U.S. patent barrier to generic amcinonide entry.
Biosimilar analysis is irrelevant because amcinonide is a small-molecule corticosteroid.
Current competitive risk is driven by FDA approval, topical product quality, formulation performance, manufacturing capability, pricing, and generic substitution.

Frequently Asked Questions

Is amcinonide still protected by a U.S. composition patent?

No current protection follows from Patent 4,158,055. The supplied claims are treatment claims, and the patent expired in 1996.

Does a 0.1% amcinonide cream fall within claim 7?

Yes. A 0.1% topical amcinonide product falls within the stated concentration range of about 0.01% to about 0.50%, subject to the other claim elements.

Does Patent 4,158,055 cover non-topical amcinonide products?

No. The claims require topical administration. They do not cover oral, injectable, or other non-topical administration.

Can a generic manufacturer avoid claims 2 through 6 by changing the cream base?

Changing the cream base would not necessarily avoid claim 2 because claim 2 is a method claim directed to use of a topical cream, not a composition claim limited to a particular cream formulation. The patent is expired in any event.

Does amcinonide require a biosimilar application?

No. Amcinonide is a small-molecule drug. A conventional generic pathway, typically an ANDA where applicable, is the relevant regulatory framework.

References

United States Patent No. 4,158,055. (1979). United States Patent and Trademark Office.
35 U.S.C. §§ 154, 271.
U.S. Food and Drug Administration. (n.d.). Amcinonide topical drug labeling and product information. Drugs@FDA.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations. Orange Book.
U.S. Food and Drug Administration. (2022). Product-specific guidance documents for generic drug development: Topical dermatological drug products.
Federal Food, Drug, and Cosmetic Act, 21 U.S.C. § 355(j).

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	7073674	⤷ Start Trial
Belgium	818929	⤷ Start Trial
Switzerland	601353	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 4,158,055

Summary for Patent: 4,158,055