United States Drug Patent 6,319,913: Claim Scope, Patent Landscape, and Generic Entry Risk

US Patent 6,319,913 covers methods for administering testosterone, estradiol, and specified derivatives through topical compositions containing oleic acid, a short-chain alcohol, and a glycol. The broadest claims are method claims, not composition claims. A potentially infringing product must therefore be used or marketed for topical administration in a manner that satisfies the claimed formulation and concentration limitations.

The patent’s commercial relevance depends on four factors: whether the patent term remains enforceable, whether the claims are listed against an FDA-approved product, whether a marketed formulation satisfies every limitation, and whether a generic or competing product has a non-infringing use or formulation.

What does US Patent 6,319,913 claim?

The claims cover two principal inventions:

Increased penetration of testosterone or estradiol through topical administration.
Reduced inflammation associated with topical application of those agents.

The claims require a composition containing:

Testosterone, estradiol, a derivative, or a mixture.
Oleic acid as a membrane fluidizer.
A C1-C4 alcohol in claims 1-18, or a C3 alcohol in claims 19-26.
A glycol, generally propylene glycol in the narrower claims.
A pH of about 4 to about 8 in claims 1-18.
Optional gelling and irritation-reducing agents in dependent claims.

The patent does not claim every testosterone or estradiol topical formulation. The formulation must fall within the stated concentration, excipient, and, for claims 1-18, pH limitations.

How are the 26 claims organized?

Claim group	Subject matter	Principal limitations
Claims 1-4	Increased penetration	Testosterone or estradiol at about 0.1%-2%; oleic acid, C1-C4 alcohol, glycol; pH 4-8
Claims 5-8	Reduced inflammation	Same core formulation, used for reducing inflammation
Claims 9-13	Narrow formulation limitations	pH 4.5-6.5; selected concentrations; isopropanol; propylene glycol; Carbopol 1342
Claims 14-18	Additional agents and hormone combinations	Irritation-reducing agent; testosterone and estradiol mixtures
Claims 19-21	Testosterone formulations	Testosterone or derivative at about 0.1%-2%; oleic acid, C3 alcohol, propylene glycol
Claims 22-26	Estradiol formulations	Estradiol or derivative at about 0.1%-10%; oleic acid, C3 alcohol, propylene glycol

Claims 1 and 5 are the principal independent claims for the first claim family. Claims 19 and 22 are separate independent claims with materially different limitations.

What is the scope of independent claim 1?

Claim 1 requires all of the following:

A method of administering a topically or systemically active agent with increased penetration.
Topical administration to a mammal.
A composition containing testosterone, estradiol, a derivative, or a mixture.
Active-agent concentration of about 0.1% to about 2%.
A penetration-enhancing system consisting essentially of:
- Oleic acid;
- A C1-C4 alcohol; and
- A glycol.
Composition pH of about 4 to about 8.

The claim is broad in the choice of alcohol and glycol. “C1-C4 alcohol” can encompass methanol, ethanol, propanol, isopropanol, butanol, and related positional isomers, subject to the claim’s construction and the specification. Claim 11 narrows the alcohol to isopropanol. Claim 12 narrows the glycol to propylene glycol.

The phrase “consisting essentially of” is significant. It generally permits additional ingredients that do not materially affect the basic and novel characteristics of the penetration-enhancing system, while excluding components that materially change those characteristics. The wording is narrower than “comprising” but broader than “consisting of.” The infringement analysis would turn on the function and effect of any additional enhancer, solvent, surfactant, or permeation modifier. See 35 U.S.C. §§ 271, 282.

What is the scope of claim 5 for inflammation reduction?

Claim 5 is structurally similar to claim 1 but changes the claimed result. It requires topical administration of the specified composition “thereby reducing inflammation associated with a topical application.”

This limitation creates a potential proof issue. A product may contain the claimed ingredients, but infringement still depends on the claimed method of use. Evidence could include:

Product labeling or prescribing information.
Promotional statements describing reduced irritation or inflammation.
Clinical data.
Instructions directing use of the composition for a topical condition.
Actual use evidence in a litigation setting.

Claims 16 and 17 narrow claim 5 to testosterone or a testosterone-estradiol mixture. Claims 6, 7, and 8 add a gelling agent and narrow the active agent, ultimately to testosterone propionate.

How do claims 19 and 22 differ from claims 1 and 5?

Claims 19 and 22 create a second, more focused claim family.

Claim 19: testosterone

Claim 19 requires:

Testosterone or a derivative.
Concentration of about 0.1% to about 2%.
Oleic acid.
A C3 alcohol.
Propylene glycol.
Topical administration to a mammal.
Increased penetration.

Unlike claims 1-18, claim 19 does not expressly recite a pH range. It also uses “comprising” rather than “consisting essentially of” for the penetration-enhancing system. That makes claim 19 potentially broader with respect to additional formulation ingredients.

Claim 20 narrows the concentration to one of five listed values: 0.5%, 1.00%, 1.25%, 1.50%, or 2.00%. Claim 21 adds a gelling agent.

Claim 22: estradiol

Claim 22 requires:

Estradiol or a derivative.
Concentration of about 0.1% to about 10%.
Oleic acid.
A C3 alcohol.
Propylene glycol.
Topical administration.
Increased penetration.

Claims 23-25 narrow the estradiol concentration. Claim 26 adds a gelling agent.

Claim 22 is materially broader in active-agent concentration than claim 19. A composition containing 3% estradiol, for example, could fall within claim 22 but outside claims 1-18 and 19-21 because those claims generally cap the active concentration at about 2%.

What formulations are protected by US 6,319,913?

The clearest formulation combinations covered by the claims include:

Active agent	Concentration	Alcohol	Glycol	Other required elements
Testosterone	0.1%-2%	Any C1-C4 alcohol under claims 1-18	Any glycol	Oleic acid; pH 4-8
Testosterone	Listed concentrations under claim 20	C3 alcohol	Propylene glycol	Oleic acid
Estradiol	0.1%-10%	C3 alcohol	Propylene glycol	Oleic acid
Estradiol	0.1%-5% under claim 23	C3 alcohol	Propylene glycol	Oleic acid
Estradiol	1%-2% under claim 24	C3 alcohol	Propylene glycol	Oleic acid
Testosterone propionate	0.1%-2% under claims 4 and 8	C1-C4 alcohol	Glycol	Oleic acid; pH 4-8

A formulation lacking oleic acid generally falls outside the literal scope of the asserted claims. A formulation using a non-glycol co-solvent may also avoid the claims, depending on whether the substituted ingredient qualifies as a glycol or is equivalent to one.

How strong is the patent estate based on the supplied claims?

The patent has several strengths:

It covers both testosterone and estradiol.
It includes broad Markush language for derivatives and mixtures.
It claims both penetration enhancement and inflammation reduction.
It includes a separate testosterone family and a separate estradiol family.
It claims concentration ranges that overlap many conventional topical hormone strengths.
Claims 19 and 22 omit the pH limitation found in claims 1-18.

The principal weaknesses are:

The claims are method claims and require topical administration.
The formulation must contain oleic acid, a qualifying alcohol, and a glycol.
Claims 1-18 require a pH between about 4 and about 8.
Claims 1-18 use “consisting essentially of,” which may restrict additional excipients.
The active-agent concentration limitations create design-around opportunities.
The “increased penetration” and “reducing inflammation” results may create evidentiary and claim-construction disputes.
Claims directed to “derivatives” may face scope disputes over whether a specific prodrug, ester, salt, or metabolite is covered.

Patent strength therefore depends more on formulation matching than on the hormone identity alone.

When does US Patent 6,319,913 lose exclusivity?

Patent expiration cannot be determined reliably from the patent number and claims alone. The controlling date is generally 20 years from the earliest effective US nonprovisional filing date for applications subject to the modern patent-term statute, adjusted for applicable patent-term adjustment and any patent-term extension. Patent term may also be affected by continuation practice, terminal disclaimers, and regulatory extension. See 35 U.S.C. §§ 154, 156.

The patent’s issue date does not independently establish the expiration date. A current freedom-to-operate or launch analysis must use the USPTO Patent Center continuity data, the patent’s term-adjustment calculation, and any terminal-disclaimer or patent-term-extension records. A patent that has expired cannot support a new infringement action, although it may remain relevant to historical litigation, invalidity analysis, or related continuation patents.

What is the Orange Book status of US 6,319,913?

The patent number alone does not establish Orange Book listing status. Orange Book listing is product-specific and depends on whether the patent was submitted by an NDA holder for an approved drug and accepted by FDA under the applicable listing standards. FDA identifies listed patents and exclusivity information in the Approved Drug Products with Therapeutic Equivalence Evaluations. See U.S. Food and Drug Administration, Approved Drug Products with Therapeutic Equivalence Evaluations.

Because the claims are method claims, any Orange Book relevance would depend on whether they claim an approved indication or method of use for a specific NDA product. A formulation patent or a broad topical-hormone patent is not automatically listed against every testosterone or estradiol product.

An Orange Book review should distinguish:

The patent’s existence.
Whether the patent was submitted by an NDA holder.
Whether FDA listed it.
Whether the listed claims cover an approved use.
Whether the listing remains active or was removed.
Whether an ANDA applicant must make a Paragraph IV certification.

What Paragraph IV challenges could arise?

An ANDA applicant could challenge a listed patent by certifying that:

The patent is invalid.
The patent is unenforceable.
The proposed product does not infringe.

Under the Hatch-Waxman framework, a Paragraph IV notice can trigger patent litigation under 35 U.S.C. § 271(e)(2). The likely defenses and invalidity theories for this patent include:

Anticipation and obviousness

Prior art may disclose topical testosterone or estradiol compositions containing alcohols, glycols, oleic acid, and gelling agents. The key question is whether one reference discloses every limitation or whether a skilled person would have combined references with a reasonable expectation of success. See 35 U.S.C. §§ 102, 103.

Written description and enablement

The broad claims cover multiple hormones, derivatives, alcohols, glycols, concentrations, and uses. An accused party could argue that the specification does not adequately support or enable the full breadth of the Markush groups. The analysis would depend on the examples and technical disclosure in the patent, not the claims alone. See 35 U.S.C. § 112.

Indefiniteness

Potential issues include:

“About” in the concentration and pH ranges.
The meaning of “increased penetration.”
The scope of “reducing inflammation.”
The boundary of “derivatives.”
The meaning of “consisting essentially of.”
The identity of a qualifying “glycol.”

The Supreme Court’s definiteness standard asks whether the claims, read in light of the specification and prosecution history, inform a skilled person of the scope of the invention with reasonable certainty. Nautilus, Inc. v. Biosig Instruments, Inc., 572 U.S. 898 (2014).

Which companies are likely to face the patent?

Potentially affected companies would include manufacturers and marketers of:

Testosterone gels.
Compounded testosterone creams and gels.
Estradiol gels and creams.
Combination testosterone-estradiol topical products.
Transdermal hormone products using oleic acid and propylene glycol.
Products using isopropanol and Carbopol-type gelling systems.

The patent would not automatically reach every topical testosterone or estradiol product. A competing product must be compared element by element against the asserted claims. The most important screening fields are active ingredient, concentration, oleic-acid content, alcohol identity, glycol identity, pH, gelling agent, labeling, and intended use.

What generic launch scenarios exist?

Scenario 1: Patent expired

If the patent term has ended and no enforceable continuation or related patent covers the same formulation or use, the patent creates no prospective launch barrier.

Scenario 2: Patent remains enforceable but is not Orange Book listed

The patent holder could pursue ordinary patent litigation if a product infringes. The ANDA automatic-stay mechanism would not necessarily apply merely because the patent exists.

Scenario 3: Orange Book-listed method patent

An ANDA applicant could submit a Paragraph IV certification, a section viii statement where appropriate, or a Paragraph III certification if the patent remains in force and expires later. The regulatory pathway would depend on the approved labeling and the scope of the listed method.

Scenario 4: Formulation design-around

A generic could reduce risk by omitting oleic acid, replacing propylene glycol with a non-glycol vehicle, using a different alcohol, changing the active concentration, or adopting a different delivery system. These changes may affect bioavailability, local tolerability, product performance, and FDA requirements.

How does this patent compare with competing testosterone-gel patent estates?

US 6,319,913 is centered on a penetration-enhancing excipient combination. Competing testosterone-gel patents may instead focus on:

Specific gel vehicles.
Carbomer or polymer systems.
Alcohol-water ratios.
Dosage and application sites.
Metered-dose pumps.
Manufacturing processes.
Pharmacokinetic profiles.
Treatment of hypogonadism.
Product-specific labeling.

This distinction matters. A product may avoid US 6,319,913 while still infringing a separate formulation, device, method-of-use, or manufacturing patent. Conversely, a product that resembles the claimed oleic-acid/alcohol/glycol system may face risk under this patent even if it differs from a branded product’s commercial formulation.

What manufacturing and geographic barriers apply?

The supplied claims do not include a manufacturing-process limitation. They focus on composition and topical administration. Manufacturing activity alone may therefore be less relevant than sale, offer for sale, importation, or use of the claimed method. Section 271 identifies the principal US infringement categories. See 35 U.S.C. § 271.

The claims are US claims. They do not directly create rights in Europe, Canada, Japan, or other jurisdictions. Geographic analysis requires review of corresponding foreign applications, national-stage filings, granted patents, expiration dates, oppositions, and maintenance status.

Key Takeaways

US 6,319,913 claims topical administration methods for testosterone, estradiol, and derivatives.
Oleic acid is a central limitation across the principal claims.
Claims 1-18 generally require a C1-C4 alcohol, a glycol, and pH 4-8.
Claims 19-26 focus on testosterone or estradiol with oleic acid, a C3 alcohol, and propylene glycol.
Claim 22 reaches estradiol concentrations up to about 10%, materially broader than the testosterone claims.
The patent does not claim every topical hormone product.
Method-of-use limitations, including increased penetration and inflammation reduction, may materially affect infringement proof.
Orange Book status cannot be inferred from the patent number alone.
Patent expiration requires continuity, term-adjustment, terminal-disclaimer, and extension analysis.
Generic risk turns on exact formulation and labeling, not merely on the presence of testosterone or estradiol.
Related formulation, device, manufacturing, and method-of-use patents may create separate barriers after this patent is cleared.

FAQs About US Patent 6,319,913

Does a testosterone gel infringe US 6,319,913 automatically?

No. The product must satisfy every limitation of an asserted claim, including the required excipients, concentration, topical administration, and applicable pH or use limitations.

Does the patent cover estradiol creams?

It may cover an estradiol cream if the formulation contains the claimed oleic acid, C3 alcohol, and propylene glycol system and falls within the claimed concentration and method limitations.

Can a product avoid the patent by removing propylene glycol?

Claims 19-26 specifically recite propylene glycol. Removing it may avoid those claims, but claims 1-18 use the broader term “glycol,” so the substitute must be assessed against those claims separately.

Are compounded hormone preparations covered?

A compounded preparation can fall within the claims if it satisfies the formulation and method limitations. Compounding status does not by itself eliminate patent infringement risk.

Does an expired patent still matter in a generic launch review?

Yes, as a historical and landscape matter. It may identify related continuation patents, prosecution admissions, prior-art issues, or formulation strategies, even though an expired patent generally cannot support prospective infringement liability.

References

United States Patent No. 6,319,913, Methods for administering topically or systemically active agents with increased penetration. United States Patent and Trademark Office.
United States Code, Title 35, §§ 102, 103, 112, 154, 156, 271, 282.
United States Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. U.S. Department of Health and Human Services.
Nautilus, Inc. v. Biosig Instruments, Inc., 572 U.S. 898 (2014).
United States Food and Drug Administration. (2024). Guidance for industry: 180-day exclusivity when multiple ANDAs are submitted on the same day. U.S. Department of Health and Human Services.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	418988	⤷ Start Trial
Australia	1313299	⤷ Start Trial
Australia	747041	⤷ Start Trial
Brazil	9814014	⤷ Start Trial
Canada	2309688	⤷ Start Trial
China	1172674	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,319,913

Summary for Patent: 6,319,913