United States Patent 4,957,730: Scope, Claims, Expiration, and Ciclopirox Nail-Varnish Patent Landscape

U.S. Patent No. 4,957,730 covers antifungal nail varnishes containing a water-insoluble film-forming substance and a substituted 1-hydroxy-2-pyridone antimycotic, including ciclopirox-type compounds. The patent issued on September 18, 1990, and its ordinary U.S. patent term expired on September 18, 2007. It therefore creates no current U.S. exclusionary right, cannot block a modern generic launch, and is not a live basis for a Paragraph IV challenge.

The patent remains commercially relevant because it identifies the core formulation concept later used in ciclopirox nail lacquer products, including 8% ciclopirox topical solutions. Current competitive protection depends on later formulation, manufacturing, regulatory, and product-specific patents rather than U.S. Patent 4,957,730.

What does U.S. Patent 4,957,730 protect?

The patent protects a nail varnish composition with two required elements:

A water-insoluble film-forming substance.
An antimycotic 1-hydroxy-2-pyridone compound meeting defined structural limitations.

The independent composition claim uses the transitional term “comprising.” That wording generally permits additional ingredients, including solvents, plasticizers, adhesion promoters, stabilizers, penetration enhancers, and other excipients, provided the claimed elements are present.

The independent method claim covers applying the claimed nail varnish to a nail affected by onychomycosis.

Core claim limitations

Claim element	Scope
Dosage form	Nail varnish
Vehicle requirement	Water-insoluble film-forming substance
Active ingredient	1-hydroxy-2-pyridone antimycotic
R1 substituent	Hydrocarbon group containing six to nine carbon atoms
R1 exclusions	No olefinic or acetylenic bonds
R2 and R4	One is hydrogen; the other is hydrogen, methyl, or ethyl
R3	Alkyl group containing up to two carbon atoms
Active form	Free compound or salt
Quantity	Effective against nail mycoses
Method claim	Application to a nail infested with onychomycosis

The composition claims are narrower than a generic claim to any antifungal nail lacquer. A product must contain the specified chemical class and structural substituents, not merely any antimycotic.

Which commercial antifungal does the patent most closely cover?

The patent most closely maps to ciclopirox and closely related 1-hydroxy-2-pyridone derivatives.

Ciclopirox is commonly identified as 6-cyclohexyl-1-hydroxy-4-methylpyridin-2-one. Its structure fits the patent’s principal embodiments involving:

A cyclohexyl R1 group.
A methyl-substituted pyridone ring.
A 1-hydroxy-2-pyridone pharmacophore.
Use in free or salt form.

The patent also claims related compounds with noncyclic C6-C9 hydrocarbon groups and an octyl embodiment. Claims 9 through 12 specifically address an octyl group, including the branched group described in the claims.

Relationship to ciclopirox olamine

The claims expressly permit the antimycotic ingredient to be present as a salt. That language is broad enough to encompass salt forms of the claimed 1-hydroxy-2-pyridone compounds, subject to the precise identity and structure of the salt and the scope of the issued claim.

Ciclopirox olamine is primarily used in creams, shampoos, gels, and lotions. Ciclopirox nail lacquer products generally use ciclopirox as the active pharmaceutical ingredient rather than relying on the olamine salt. The patent’s salt language therefore has wider relevance than the later commercial nail-lacquer product alone.

How broad is claim 1?

Claim 1 is the controlling claim. It reaches any nail varnish that contains all of the following:

A water-insoluble film former.
A qualifying 1-hydroxy-2-pyridone compound.
An R1 hydrocarbon substituent with six to nine carbon atoms.
No olefinic or acetylenic bonds in R1.
The specified R2, R3, and R4 substituent pattern.
An amount effective against nail mycoses.

The claim is composition-focused. It does not require a specific concentration, solvent system, drying time, viscosity, package, brush, or treatment schedule.

The phrase “an amount effective against nail mycoses” imposes a functional limitation. In practice, the limitation would be assessed using the product’s formulation, labeling, pharmacology, clinical evidence, and the ordinary meaning of therapeutic effectiveness.

Because the claim does not specify a particular film former, multiple formulation platforms could fall within its literal scope. The claim can reach solvent-based lacquers, polymeric films, and other water-insoluble coating systems if the remaining limitations are satisfied.

What the claim does not cover

Claim 1 does not literally cover every antifungal nail product. It excludes products that lack:

A qualifying 1-hydroxy-2-pyridone.
The required C6-C9 hydrocarbon R1 group.
The required substituent arrangement.
A water-insoluble film-forming substance.
A therapeutic amount effective against nail mycoses.

Products based on amorolfine, efinaconazole, tavaborole, terbinafine, or luliconazole are not within the literal chemical scope of claim 1 merely because they are antifungal nail treatments.

What do claims 2 through 20 add?

Claims 2 through 20 create nested limitations directed to chemical identity, substitution pattern, and concentration.

Claims	Added limitation
2	R2 and R4 are both hydrogen
3, 6	R1 contains a cyclic group
4, 7	The cyclic group is cyclohexyl
5	R1 is cyclohexyl
8	Cyclohexyl R1 with additional ring-substitution limitations
9, 10	R1 is octyl
11, 12	Specific branched octyl structure
13	2% to 80% by weight of nonvolatile components
14	10% to 60% by weight of nonvolatile components
15	20% to 40% by weight of nonvolatile components
16	0.5% to 20% by weight
17	2% to 15% by weight
18	At least 4% by weight in a medicated nail varnish
19	Less than 4% by weight
20	At least 1% by weight

The concentration claims use two different measurement bases:

Claims 13 through 15 measure the active against nonvolatile components.
Claims 16 through 20 state the active concentration by total weight.

Those bases are not interchangeable. A formulation can satisfy one concentration claim while failing another.

Concentration scope

Claim 1 has no numerical concentration limitation. Claims 13 through 20 therefore narrow claim 1 rather than define the minimum concentration necessary for infringement of the independent composition claim.

A product containing 8% ciclopirox would fall within the numerical ranges of claims 16, 17, and 20, assuming the total-weight calculation is used. It could also fall within claims 13 through 15 depending on the amount of nonvolatile material in the formulation.

Internal wording issue in claim 8

The supplied wording of claim 8 states that R1 is cyclohexyl and R2 and R3 are hydrogen. Claim 1, however, states that R3 is alkyl containing up to two carbon atoms, which may create an apparent inconsistency if “alkyl” is read as excluding hydrogen.

That issue should be analyzed against the issued patent text, including the chemical formula, specification, prosecution history, and any correction certificate. The claim hierarchy cannot be assessed solely from an OCR or transcription error in a reproduced claim set. The broader claim analysis remains intact because claims 1 through 7 and 9 through 20 independently define relevant species and formulations.

What does claim 21 protect?

Claim 21 is a method-of-treatment claim covering application of the claimed nail varnish to a nail affected by onychomycosis.

The method claim requires:

A nail affected by onychomycosis.
Application of a nail varnish meeting claim 1.
An effective amount of the claimed compound.

The method claim does not state a particular frequency of application, duration of treatment, nail preparation procedure, or use with debridement. Those details could be supplied by labeling or clinical practice without appearing in the claim.

Claim 21 would have been relevant to direct use infringement during the patent term. It is no longer enforceable because the patent expired in 2007.

When did U.S. Patent 4,957,730 expire?

The patent issued on September 18, 1990. For a U.S. patent issued before the June 8, 1995 transition date, the standard term was generally 17 years from issue, subject to terminal disclaimers, reexamination adjustments, or other term-specific events.

On that basis, the patent expired on September 18, 2007.

Event	Date
U.S. patent issue	September 18, 1990
Ordinary 17-year term	September 18, 2007
Current enforceability	Expired
Current Paragraph IV relevance	None for this patent
Current generic blocking power	None

The patent’s expiration means that a manufacturer does not need a license from the patent owner to practice the claimed nail-varnish composition in the United States.

What is the FDA and Orange Book status of the patent?

U.S. Patent 4,957,730 is not a current Orange Book barrier to ciclopirox nail-lacquer products.

The FDA approved Penlac, an 8% ciclopirox topical solution, for onychomycosis. FDA-approved labeling identifies ciclopirox as the active ingredient and describes application to affected toenails and fingernails.[2] FDA Orange Book listings concern patents submitted for approved drug products and listed as relevant to approved indications, formulations, or methods.[3]

The practical regulatory position is:

U.S. Patent 4,957,730 is expired.
It cannot support a current 30-month stay.
It cannot support a current Paragraph IV notice.
It cannot prevent approval of an ANDA.
It cannot require a generic applicant to certify that the patent is invalid or not infringed.
Any current patent dispute would have to involve a later, unexpired patent.

An ANDA applicant for an approved ciclopirox nail-lacquer product could rely on an expired-patent certification or otherwise treat the patent as nonblocking under the Hatch-Waxman framework. The exact certification depends on the Orange Book listing history and the applicant’s product and labeling.

What later patents and rights matter for ciclopirox nail lacquer?

The post-1990 commercial landscape shifted from broad active-ingredient and nail-varnish concepts to narrower product protection.

Formulation patents

Later formulation patents may address:

Specific polymeric film formers.
Hydroxypropyl chitosan or other adhesion systems.
Solvent ratios.
Improved nail penetration.
Reduced drying time.
Removal properties.
Stability and crystallization control.
Packaging and applicator systems.
Combination treatment with mechanical debridement.
Specific concentrations, dosing schedules, or treatment durations.

A later formulation patent can remain relevant even if it uses ciclopirox, because the patent may claim a particular excipient combination or manufacturing process rather than the active ingredient itself.

Method-of-use patents

Method claims may cover:

Treatment of toenail versus fingernail disease.
Specific application frequency.
Treatment after nail debridement.
Use with defined degrees of nail involvement.
Treatment of subungual infection.
Specific treatment durations or maintenance regimens.

A generic manufacturer can often avoid method-of-use infringement through a section viii statement or a skinny label if the patented use is carved out and the remaining labeling does not encourage the patented method. The availability of that strategy depends on the Orange Book listing and the claim language.

Manufacturing and process rights

Manufacturing patents can create a separate barrier where they claim:

Preparation of high-purity ciclopirox.
Crystallization or particle-size control.
Production of the film-forming polymer.
Mixing order and temperature controls.
Solvent-removal processes.
Filling and packaging of volatile nail-lacquer products.

These rights generally do not block all products containing ciclopirox. They constrain particular manufacturing routes or processes.

Which companies compete with ciclopirox nail lacquer?

Ciclopirox competes in topical onychomycosis against both branded and generic products.

Product	Active ingredient	FDA pathway	Competitive distinction
Penlac and authorized/generic equivalents	Ciclopirox 8%	NDA and ANDA	Established nail-lacquer platform
Jublia	Efinaconazole 10%	NDA	Topical solution with different active and delivery profile
Kerydin	Tavaborole 5%	NDA	Topical solution with boron-containing antifungal
Amorolfine products outside the U.S.	Amorolfine	National or regional approvals	Widely used non-U.S. lacquer product
Oral terbinafine	Terbinafine	NDA and generic	Systemic treatment with different safety and monitoring profile

Efinaconazole and tavaborole do not fall within the chemical limitations of U.S. Patent 4,957,730. Their patent estates were developed independently and include product, formulation, method, and regulatory-exclusivity rights specific to those active ingredients.

Which companies challenged the patent through Paragraph IV?

U.S. Patent 4,957,730 is too old to support a current Paragraph IV challenge. Any Paragraph IV certification directed to this patent would have had to occur before its 2007 expiration.

The relevant modern generic competition concerns later patents and regulatory exclusivity associated with ciclopirox products, not the expired patent itself. Generic manufacturers may file ANDAs for ciclopirox 8% topical solution products, subject to FDA requirements for pharmaceutical equivalence, bioequivalence where applicable, chemistry and manufacturing controls, and labeling.

The patent does not create a current litigation risk for a manufacturer launching a ciclopirox nail lacquer.

What licensing deals are associated with the patent?

The patent reflects the early proprietary development of 1-hydroxy-2-pyridone antifungal chemistry and nail-varnish delivery. Commercial rights for Penlac and related products were held and marketed through successor pharmaceutical companies, including Dermik and Sanofi-related entities.

A patent assignment or brand commercialization arrangement does not establish that a later generic manufacturer requires a license. Because U.S. Patent 4,957,730 expired in 2007, any historical license covering that patent has no current exclusivity effect against independent practice of the claimed invention.

Current licensing value would instead arise from:

Unexpired formulation patents.
Manufacturing know-how.
Regulatory data rights.
Trademark rights.
Trade secrets.
Distribution agreements.
Device or packaging technology.

How strong is the patent estate today?

The patent estate represented by U.S. Patent 4,957,730 has no current blocking strength in the United States.

Risk category	Current assessment
Active-ingredient patent risk	None from this patent
Nail-varnish formulation risk	None from this patent
Method-of-use risk	None from this patent
Paragraph IV risk	None from this patent
Biosimilar risk	Not applicable
Generic launch risk	Low based on this patent
Freedom-to-operate value	Historical only
Commercial exclusivity value	None after expiration

The patent may remain relevant for prior-art analysis, validity disputes involving later patents, and historical freedom-to-operate reviews. It cannot restore exclusivity to ciclopirox or prevent a competing formulation.

What generic launch scenarios exist?

A generic manufacturer can pursue several commercial strategies:

Direct 8% ciclopirox equivalent

The most direct route is an 8% ciclopirox nail-lacquer product with equivalent active strength, dosage form, route, and labeling. The expired patent does not block this route.

Reformulated ciclopirox lacquer

A manufacturer may use a different film former, solvent system, or packaging configuration. Such a product may avoid later formulation patents while retaining the established ciclopirox active ingredient.

Lower-concentration product

Claims 16 through 20 include several concentration ranges, but those claims expired with the patent. A lower-concentration product does not face a current restriction from this patent.

Non-ciclopirox antifungal

Efinaconazole, tavaborole, amorolfine, and other actives fall outside the structural limitations of the patent. Their market access depends on their own patent and regulatory landscape.

What geographic protection did the patent provide?

U.S. Patent 4,957,730 provided rights only in the United States. Equivalent applications or patents in Europe, Canada, Japan, and other jurisdictions would have had separate terms, prosecution histories, claim scopes, and expiration dates.

The U.S. expiration does not establish that corresponding foreign patents expired on the same date. A global freedom-to-operate review must examine each national family member and any supplementary protection certificate, patent-term extension, pediatric extension, or terminal disclaimer.

For U.S. commercial planning, however, the relevant conclusion is direct: the named U.S. patent expired in 2007.

Key Takeaways

U.S. Patent 4,957,730 covers nail varnishes containing a water-insoluble film former and specified 1-hydroxy-2-pyridone antifungals.
The principal commercial relevance is ciclopirox-type nail lacquer.
Claim 1 is broad as to the film former but narrow as to chemical structure.
Claims 2 through 20 narrow the invention by substituent pattern and concentration.
Claim 21 covers treatment of onychomycosis using the claimed varnish.
The patent issued on September 18, 1990, and expired on September 18, 2007.
It is no longer an Orange Book or Paragraph IV barrier.
It provides no current protection against generic ciclopirox nail-lacquer products.
Current commercial risk must be assessed against later formulation, method, manufacturing, packaging, and regulatory rights.
Efinaconazole, tavaborole, amorolfine, and terbinafine are outside the literal chemical scope of this patent.
Biosimilar analysis is not applicable because ciclopirox is a small-molecule drug.

FAQs

Does U.S. Patent 4,957,730 cover Penlac?

It covers the core concept of a nail varnish containing a qualifying 1-hydroxy-2-pyridone antifungal, which is consistent with ciclopirox nail-lacquer technology. It does not provide current protection because it expired in 2007.

Can a generic company launch ciclopirox nail lacquer without a license to this patent?

Yes. The patent is expired and no longer prevents manufacture, FDA approval, or sale of a ciclopirox nail-lacquer product in the United States.

Does the patent cover efinaconazole or tavaborole?

No. Those products use different active ingredients and do not satisfy the claimed 1-hydroxy-2-pyridone structural limitations.

Is ciclopirox nail lacquer a biosimilar product?

No. Ciclopirox is a chemically synthesized small-molecule drug. A competing product would generally proceed through the generic-drug framework, not the biosimilar pathway.

Can a later patent still affect a ciclopirox generic launch?

Yes. A later patent may claim a particular formulation, excipient system, manufacturing process, dosing regimen, package, or method of use. Those rights must be evaluated independently from U.S. Patent 4,957,730.

References

U.S. Patent No. 4,957,730. (1990, September 18). Nail varnish. United States Patent and Trademark Office.
U.S. Food and Drug Administration. (1999). Penlac nail lacquer, ciclopirox 8% topical solution prescribing information. FDA.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.
U.S. Food and Drug Administration. (2024). Approved drug products and abbreviated new drug application database. FDA.
U.S. Code, 35 U.S.C. § 154. Patent term.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Germany	3544983	Dec 19, 1985

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	53292	⤷ Start Trial
Australia	587883	⤷ Start Trial
Australia	6670786	⤷ Start Trial
Canada	1283054	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Summary for Patent: 4,957,730