United States Patent 5,607,979: Scope, Claim Construction, Expiration, and Patent Landscape

U.S. Patent No. 5,607,979 covers a topical skin-protectant dispersion containing 35% to approximately 50% finely divided polytetrafluoroethylene, or PTFE, dispersed in a liquid perfluorinated polyether, or PFPE, with a viscosity of 20 to 350 cSt. The patent also covers narrower PTFE particle and surface-area specifications and a high-shear manufacturing process. The patent issued on March 4, 1997. Based on the pre-1995 filing regime applicable to this patent family, its ordinary 17-year term would have expired on March 4, 2014, absent patent-term adjustment, extension, or a terminal disclaimer. The claims therefore do not provide a current U.S. blocking right.

What does U.S. Patent 5,607,979 protect?

The patent protects a two-phase topical composition in which finely divided PTFE is dispersed through liquid PFPE. The central technical concept is a high-solids fluoropolymer dispersion intended to form a protective barrier on skin.

The independent composition limitations are:

Limitation	Required scope
Product type	Topical skin protectant composition
PTFE concentration	At least 35% to about 50% by weight
PTFE form	Finely divided PTFE
PTFE surface area	Below about 6 m²/g
Carrier	Liquid perfluorinated polyether
Carrier viscosity	About 20 cSt to about 350 cSt
Physical state	Dispersion
Additional process claim	High-shear mixing of the specified ingredients

Claims 1 and 6 are materially identical based on the claim text supplied. Each requires the same PTFE concentration, PTFE surface-area limit, PFPE carrier, and viscosity range. The duplication may reflect claim drafting or prosecution history, but it does not create a materially different composition scope on the face of the claims.

How should the composition claims be construed?

“Comprises” creates an open-ended formulation claim

Claims 1 and 6 use “comprises.” The claims therefore permit additional ingredients, provided the accused product still contains the claimed PTFE and PFPE components within the required parameters. Possible additional ingredients could include emollients, pigments, preservatives, antioxidants, fragrances, solvents, or other dermatological excipients.

The presence of additional ingredients would not, by itself, avoid the claims. The principal formulation questions would be:

Whether the product contains PTFE at the claimed concentration.
Whether the liquid carrier is a PFPE.
Whether the PFPE has the claimed viscosity.
Whether the PTFE qualifies as finely divided and has the required surface area.
Whether the PTFE is dispersed rather than merely suspended in a different phase.

The 35% to about 50% PTFE range is a major limitation

A product containing materially less than 35% PTFE would ordinarily fall outside the literal scope of claims 1 and 6. A product with more than approximately 50% PTFE may also fall outside the literal range, although the meaning of “about 50%” would depend on intrinsic evidence, prosecution history, technical evidence, and the degree of variation accepted in the relevant industry.

The concentration must be measured on a consistent weight basis. The patent claims do not specify whether the percentage is calculated against the full finished composition, the PTFE-PFPE phase, or another formulation basis. The specification and prosecution record would control that issue.

“Below about 6 m²/g” is not equivalent to ordinary PTFE identification

The claim requires a PTFE powder with a surface area below approximately 6 m²/g. This limitation distinguishes the claimed material from higher-surface-area PTFE grades and creates a product-characterization issue in enforcement or freedom-to-operate analysis.

Surface area can depend on:

Measurement method.
Sample preparation.
Particle morphology.
Porosity.
Agglomeration.
Lot variation.
Whether the reported value is a supplier specification or a measured batch result.

The narrower claims require a surface area below approximately 4 m²/g.

What do claims 2 through 5 and 7 through 10 add?

Claims 2 through 5 and 7 through 10 narrow the composition claims through PTFE particle-size and surface-area requirements.

Claims	Added limitation
2 and 7	At least 90% of PTFE particles have a particle size below 5 microns
3 and 8	PFPE is based on perfluoropropylene oxide
4 and 9	PTFE surface area is below about 4 m²/g
5 and 10	PTFE surface area below about 4 m²/g plus at least 90% below 5 microns

The narrowest composition claims, 5 and 10, require all of the following:

35% to approximately 50% PTFE.
PTFE surface area below approximately 4 m²/g.
At least 90% of the PTFE below 5 microns.
PFPE carrier viscosity of approximately 20 to 350 cSt.
A topical skin-protectant dispersion.

These claims may be more difficult to prove in practice because they require particle-size distribution and surface-area testing in addition to formulation analysis.

What does the process claim cover?

Claim 11 covers a process for preparing the composition by subjecting the specified PTFE-PFPE mixture to high-shear mixing.

The process claim requires:

PTFE concentration of at least 35% to approximately 50%.
PTFE surface area below approximately 6 m²/g.
A PFPE carrier.
PFPE viscosity of approximately 20 to 350 cSt.
High-shear mixing.

The claim does not state a specific shear rate, impeller geometry, mixing duration, temperature, pressure, or equipment type. Those omissions broaden the process language but create potential disputes over what qualifies as “high shear.”

A manufacturer could face process-claim issues even if the final composition is not sold with a complete formulation disclosure. Evidence could include batch records, equipment specifications, manufacturing instructions, process validation documents, and source-code or technical files describing mixing conditions.

What is the likely patent expiration date?

U.S. Patent No. 5,607,979 issued on March 4, 1997. For a patent subject to the pre-June 8, 1995 U.S. patent-term regime, the ordinary term was 17 years from issuance. On that basis:

Event	Date
Patent issuance	March 4, 1997
Ordinary 17-year expiration	March 4, 2014
Current enforceability under ordinary term	Expired

Patent-term adjustment generally became relevant to later-filed applications under the American Inventors Protection Act. The supplied claim text does not establish any term adjustment, patent-term extension, reissue, or terminal disclaimer. None would ordinarily be expected to extend a topical formulation patent of this type into the current period.

Because the patent’s ordinary term expired in 2014, a new U.S. product launch would not ordinarily face infringement liability based solely on these claims. Separate later patents could still matter if they cover a particular commercial product, packaging system, manufacturing method, indication, or formulation.

Is U.S. Patent 5,607,979 listed in the Orange Book?

The patent is unlikely to have an Orange Book listing because the claims cover a topical skin-protectant composition rather than an approved prescription drug product submitted under an NDA.

The FDA Orange Book primarily identifies patents and regulatory exclusivities associated with approved drug products. A topical barrier product marketed as an OTC skin protectant, cosmetic, medical device, or specialty industrial formulation would not automatically receive Orange Book treatment. The patent number and claims alone do not establish an Orange Book listing. [2]

The practical implications are:

No Orange Book patent certification should be assumed.
A Paragraph IV challenge would generally not be the principal pathway for attacking this patent.
FDA approval status and patent status are separate issues.
The existence of the patent did not itself establish an FDA-approved indication.

When would a Paragraph IV challenge apply?

A Paragraph IV certification is generally used when an abbreviated new drug application applicant challenges a patent listed in the FDA Orange Book for a reference-listed drug. [2] The claimed product here does not appear to be an Orange Book-listed prescription drug product.

Accordingly, a conventional Paragraph IV pathway is not the expected mechanism for challenging U.S. Patent 5,607,979. If the patent had remained in force, potential mechanisms could have included:

Declaratory judgment litigation.
Invalidity or noninfringement defenses in an infringement action.
Post-grant or inter partes review, subject to statutory timing and eligibility requirements.
A product-development strategy designed around the concentration, carrier, surface-area, or particle-size limitations.

Because the patent expired in 2014, an inter partes review or Paragraph IV strategy would generally have no commercial purpose against this patent alone.

What is the relevant patent landscape?

The relevant landscape is a formulation and materials landscape rather than a conventional small-molecule drug landscape.

Core technical categories

Category	Relevance to the patent
PTFE skin barriers	Covers the use of fluoropolymer particles as a physical protective layer
PFPE topical carriers	Covers chemically inert, highly fluorinated liquid carriers
PTFE particle engineering	Concerns particle size, surface area, morphology, and dispersion behavior
High-solids dispersions	Concerns stability, viscosity, spreadability, and film formation
High-shear manufacturing	Concerns dispersion preparation and batch reproducibility
Topical barrier formulations	Includes nonfluorinated alternatives such as silicones, hydrocarbons, waxes, and polymeric films
Medical-device or cosmetic formulations	May involve separate regulatory and patent classifications

The patent is narrow in chemical identity but broad in the central concentration window. A competing product using a silicone, hydrocarbon, fluorinated solvent, or non-PFPE carrier would not literally satisfy the PFPE limitation. A product using PTFE below 35% would generally avoid the principal composition claims, subject to doctrine-of-equivalents analysis and the prosecution history.

How strong is the patent estate?

The patent estate appears narrow and technically specific rather than broad and platform-based.

Strengths

Independent claims directly identify the key formulation architecture.
The 35% to approximately 50% PTFE range may capture high-solids commercial formulations.
The PFPE viscosity range covers a meaningful set of liquid fluorinated carriers.
Dependent claims provide fallback positions based on particle size, surface area, and PFPO-based PFPE.
Claim 11 reaches the manufacturing process, not only the finished product.

Weaknesses

The patent term has expired under the ordinary term calculation.
Claims 1 and 6 appear duplicative.
The claims use potentially disputed terms such as “finely divided,” “about,” “dispersion,” and “high shear.”
Surface-area and particle-size limitations require specialized testing.
No specific PFPE molecular-weight distribution, end group, formulation stability requirement, or shear parameter is stated.
The claim set does not cover every topical barrier product using fluorinated chemistry.
Product-by-process evidence may be difficult where the final composition can be made through multiple methods.

The patent may have been commercially useful during its term, but it is no longer a current U.S. exclusivity barrier based on the claims supplied.

What generic-entry and competitive risks exist?

The conventional generic-drug framework does not fit this patent well. The principal commercial risks would have been formulation substitution and design-around rather than an ANDA-driven generic launch.

Potential design-around routes include:

Using less than 35% PTFE.
Using more than approximately 50% PTFE, if outside the construction of “about 50%.”
Selecting a non-PFPE liquid carrier.
Using a PFPE outside the 20 to 350 cSt viscosity range.
Selecting PTFE with a surface area at or above the claimed threshold.
Using a particle-size distribution that does not meet the dependent claims.
Replacing PTFE with another fluoropolymer or nonfluorinated film-forming material.
Purchasing a pre-dispersed material and avoiding the claimed high-shear process.

These strategies require analysis of any later patent rights, trade secrets, regulatory requirements, product-performance specifications, and the doctrine of equivalents. They are not needed to avoid an expired patent.

What litigation, licensing, and settlement information is material?

The supplied claim set contains no licensing, settlement, or litigation terms. The claims alone do not establish:

Whether the patent was asserted.
Whether a license was granted.
Whether a settlement restricted commercialization.
Whether a continuation or divisional application issued.
Whether an ownership transfer occurred.
Whether any foreign counterpart remains active.

For current diligence, the relevant legal question is whether any later patent family member or unrelated patent covers the commercial formulation. U.S. Patent 5,607,979 itself does not provide an active U.S. patent right after its ordinary 2014 expiration.

Does the patent create biosimilar risk?

No. Biosimilar risk is not relevant to this patent. The claims concern a topical PTFE-PFPE composition and a mixing process. They do not claim a biologic, biosimilar reference product, therapeutic protein, antibody, or cell-based product.

What is the commercial exposure from this patent?

Direct current revenue exposure from this patent is likely zero because the ordinary patent term expired in 2014. Historical exposure would depend on whether a commercial topical protectant used:

35% to approximately 50% PTFE.
PTFE with surface area below approximately 6 m²/g.
PFPE with viscosity between approximately 20 and 350 cSt.
A high-shear manufacturing step.

Revenue exposure cannot be calculated from the claims because the patent record supplied does not identify a patentee, licensee, product, sales history, market share, or asserted commercial formulation.

Key Takeaways

U.S. Patent 5,607,979 claims a high-solids PTFE dispersion in liquid PFPE for topical skin protection.
The core composition range is 35% to approximately 50% PTFE in PFPE with 20 to 350 cSt viscosity.
Dependent claims narrow the invention by PFPO-based PFPE, PTFE surface area below approximately 4 m²/g, and particle size below 5 microns for at least 90% of particles.
Claim 11 covers high-shear preparation of the claimed dispersion.
Claims 1 and 6 appear substantively identical.
The patent issued March 4, 1997 and appears to have expired March 4, 2014 under the ordinary 17-year term.
Orange Book and Paragraph IV mechanisms are not naturally applicable to this topical protectant patent.
The patent is no longer a current U.S. exclusivity barrier, although later patents covering a commercial product must be analyzed separately.
The principal technical design-around variables are PTFE concentration, PFPE identity, PFPE viscosity, PTFE surface area, particle-size distribution, and mixing process.

FAQs

Can a company sell a PTFE-PFPE topical protectant today without licensing U.S. Patent 5,607,979?

Yes, the patent’s ordinary U.S. term appears to have expired in 2014. Separate unexpired patents, trade secrets, regulatory rights, or contractual restrictions could still affect the product.

Does using Krytox or another PFPE automatically infringe the patent?

No. The carrier must be a liquid PFPE within the claimed viscosity range, and the product must also satisfy the PTFE concentration and PTFE-property limitations. The identity of a PFPE product alone is insufficient.

Would a product containing 30% PTFE infringe the composition claims?

It would ordinarily fall outside the literal 35% minimum in claims 1 and 6. Equivalence would depend on claim construction, prosecution history, and technical evidence.

Is the high-shear mixing step required for infringement of the composition claims?

No. Claims 1 through 10 are composition claims. Claim 11 separately requires high-shear mixing. A product could potentially satisfy the composition claims without infringing claim 11 if it was made without the claimed process.

Are PTFE particle size and surface area the same measurement?

No. Particle size describes the size distribution of the particles. Surface area measures exposed surface per unit mass and can be affected by morphology, porosity, agglomeration, and measurement method. The dependent claims require separate technical showings.

References

U.S. Patent No. 5,607,979, “Topical Skin Protectant Composition,” issued March 4, 1997.
U.S. Food and Drug Administration. (2023). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book. FDA.
United States Patent and Trademark Office. (2024). Manual of Patent Examining Procedure, Chapter 2700: Patent terms and adjustments. USPTO.
35 U.S.C. §§ 154, 271, 282.
21 U.S.C. § 355(j).

Details for Patent: 5,607,979

Summary for Patent: 5,607,979