US Patent 7,608,606: Testosterone Gel Claims, Scope, Expiration, and Patent Landscape

US Patent 7,608,606 protects a specific method of treating male hypogonadism with a testosterone topical gel. The patent is narrower than a general testosterone transdermal patent because infringement requires the claimed formulation architecture, including a macrocyclic lactone identified as oxacyclohexadecan-2-one, a defined alcohol-solvent system, a thickener, pH, viscosity, and testosterone concentration ranges. The claims also include a pharmacokinetic limitation based on 24-hour serum testosterone exposure.

The patent was associated with the Testim-type testosterone gel technology and reached the end of its ordinary U.S. patent term in the 2023-2024 period, depending on the applicable patent-term calculation and any adjustment. It is not a current long-term barrier to an otherwise approvable generic formulation, although formulation-specific patents, regulatory exclusivity, litigation history, and other family members must be assessed separately.

What does US Patent 7,608,606 cover?

US 7,608,606 covers a method for maintaining therapeutically effective testosterone concentrations in a hypogonadal male by applying a defined topical gel to the skin.

The independent claim requires all of the following:

Claim element	Required limitation
Patient	Male with hypogonadism
Therapeutic objective	Maintaining a therapeutically effective serum testosterone concentration
Route	Transdermal delivery by application to the skin
Dosage form	Topical gel
Viscosity	About 2,000 to about 6,000 centipoise
pH	About 4 to about 8
Testosterone	About 0.1% to about 5% by weight
Oxacyclohexadecan-2-one	About 0.5% to about 25% by weight
Thickener	About 1% to about 6% by weight
Alcohol solvent	About 60% to about 75% by weight ethanol or isopropanol
Co-solvents	Propylene glycol and glycerin

The claim is a method claim, not merely a composition claim. A product that contains the listed ingredients may not infringe claim 1 unless it is used in the claimed manner for the claimed patient population and therapeutic purpose.

What is the role of oxacyclohexadecan-2-one?

Oxacyclohexadecan-2-one is a macrocyclic lactone used as a skin-permeation enhancer. The compound is commonly associated with pentadecalactone nomenclature in transdermal formulation work. The claim treats it as a required formulation component rather than an optional excipient.

That limitation materially narrows the patent. A testosterone gel using ethanol, propylene glycol, glycerin, and a thickener but omitting the claimed lactone would have a substantial non-infringement position under literal infringement analysis, subject to any applicable doctrine-of-equivalents issues.

How broad are the claims of US 7,608,606?

Claim 1 has moderate formulation breadth but narrow combination breadth. It allows substantial variation within each numerical range, while requiring the combination of all listed features.

The principal breadth comes from the following ranges:

Testosterone: 0.1% to 5% by weight
Oxacyclohexadecan-2-one: 0.5% to 25% by weight
Thickener: 1% to 6% by weight
Ethanol or isopropanol: 60% to 75% by weight
pH: 4 to 8
Viscosity: 2,000 to 6,000 cps

The claim uses the term “about,” which may permit modest variation around the stated numerical boundaries. The scope is not unlimited. Courts generally evaluate “about” in light of the specification, prosecution history, technical measurement methods, and the purpose of the claimed range.

What is the infringement significance of the combination requirement?

A competing product generally must satisfy every limitation of the asserted claim for literal infringement. For claim 1, a challenger would examine:

The actual quantitative composition.
The identity and concentration of the permeation enhancer.
The solvent percentages.
The thickener concentration.
The measured pH.
The measured viscosity.
The labeled or intended method of use.

A formulation can avoid literal infringement by falling outside one required limitation. The strongest design-around opportunities are likely to involve replacing the macrocyclic lactone, changing the solvent system, or using a different rheology profile.

What additional limitations do claims 2 through 8 add?

Claims 2 through 8 narrow claim 1 through dose, pharmacokinetic, and excipient limitations.

Claim	Added limitation
2	Unit dose contains 1 to 300 mg testosterone and produces a specified 24-hour AUC increase
3	Composition includes polyethylene glycol
4	Polyethylene glycol is 0.001% to 5% by weight
5	Oxacyclohexadecan-2-one is limited to 0.5% to 15% by weight
6	Claim 5 plus the claim 2 dose and AUC limitations
7	Claim 5 plus polyethylene glycol
8	Claim 7 plus polyethylene glycol at 0.001% to 5%

How significant is the AUC limitation?

Claim 2 requires that a single application of a unit dose increase the 24-hour serum testosterone exposure, measured as AUC0-24, by approximately 100 to 35,000 ng·h/dL compared with the amount that would have been achieved without administration.

This limitation creates two issues.

First, infringement may depend on pharmacokinetic evidence rather than formulation analysis alone. A generic applicant could argue that its product does not meet the claimed AUC range, although the product’s clinical or bioequivalence data could provide evidence against that position.

Second, the comparator is a no-dose baseline for the same 24-hour period. The claim does not simply require a target serum concentration. It requires a specified increase in exposure following the unit-dose application.

Claims 3, 4, 7, and 8 are narrower and have greater vulnerability to design-around because polyethylene glycol must be present in the specified concentration range.

What patents protect Testim and related testosterone gels?

US 7,608,606 should be analyzed with related testosterone-gel patents, particularly US 6,818,226, which is associated with testosterone gel formulation technology and was relevant to the Testim product patent estate.

Patent	Relevance
US 6,818,226	Earlier testosterone gel formulation and delivery technology associated with the Testim product family
US 7,608,606	Method of treating hypogonadism using a testosterone gel containing oxacyclohexadecan-2-one and defined solvent and viscosity parameters
US 7,608,606 dependent claims	Dose, AUC, polyethylene glycol, and narrower permeation-enhancer limitations

The relevant estate is formulation-specific rather than molecule-specific. Testosterone itself is an old active pharmaceutical ingredient and cannot support modern product exclusivity. Commercial protection instead depends on formulation, delivery, dosing, manufacturing, labeling, and regulatory barriers.

What formulations are protected by US 7,608,606?

The claim targets a gel with:

A high alcohol fraction, using ethanol or isopropanol.
Propylene glycol and glycerin as co-solvents.
A thickener at 1% to 6%.
A macrocyclic lactone permeation enhancer.
A viscosity within the claimed 2,000-6,000 cps range.
A mildly acidic to mildly alkaline pH.
Testosterone within the claimed concentration range.

A conventional testosterone gel lacking the claimed lactone is outside the most important structural limitation. Conversely, a product that uses the same enhancer but changes the alcohol content, thickener, or viscosity may avoid literal infringement if the difference is meaningful and outside the “about” range.

When did US Patent 7,608,606 expire?

The patent issued on October 27, 2009. Its ordinary term was calculated under the post-1995 U.S. patent-term regime, measured principally from the earliest effective nonprovisional filing date rather than from the grant date.[1]

Public patent records place the relevant term in the 2023-2024 period. The patent therefore does not provide a continuing 20-year exclusionary period against current generic testosterone-gel development. Any patent-term adjustment, terminal disclaimer, maintenance-fee event, or related continuation must be checked against the official USPTO record when determining a litigation or launch date.

Patent expiration does not eliminate all commercial barriers. A product may still face:

A later-expiring formulation patent.
A method-of-use patent.
FDA approval requirements.
Manufacturing know-how and stability requirements.
Restricted-use or labeling issues.
Patent litigation based on related family members.

What was the FDA and Orange Book status of the related product?

Testosterone topical gels are prescription products regulated under an FDA new drug application. Testim was approved under NDA 021902 and was associated with Auxilium Pharmaceuticals before the company’s acquisition by Endo Pharmaceuticals.[2]

The FDA Orange Book is the principal source for listed patents and pediatric-exclusivity information for approved small-molecule drug products.[3] Orange Book-listed patents can support a Paragraph IV certification and patent litigation under the Hatch-Waxman Act.

The Orange Book analysis should distinguish among:

Patents listed for the reference listed drug.
Patents that have expired.
Patents delisted or removed after regulatory or judicial proceedings.
Patents that remain listed but do not cover the proposed generic’s formulation or labeling.
Unlisted patents that may still be asserted outside the statutory Orange Book framework.

US 7,608,606 was principally important during the period when Testim and related testosterone gels had active U.S. patent protection. Its practical value against current generic entry is limited by the end of the patent term.

Which companies challenged testosterone gel patents?

The competitive field has included branded testosterone-gel developers, generic manufacturers, and specialty pharmaceutical companies.

Company or group	Relevant position
Auxilium Pharmaceuticals	Original commercial sponsor associated with Testim
Endo Pharmaceuticals	Successor commercial owner following acquisition of Auxilium
AbbVie	Sponsor of AndroGel, a competing testosterone gel
Perrigo and other generic manufacturers	Participants in generic testosterone-gel development and FDA approval activity
Authorized or licensed distributors	Potential commercial channels for generic or authorized-generic products

Paragraph IV challenges are product-specific. A generic applicant must certify against each listed patent and may assert that a patent is invalid, unenforceable, or not infringed. A Paragraph IV notice can trigger a 30-month stay of FDA approval under the Hatch-Waxman framework if the NDA holder or patent owner files an infringement action within the statutory period.[4]

The presence of a Paragraph IV filing does not establish that the patent is weak. The commercial outcome depends on claim construction, formulation testing, prosecution history, validity defenses, and settlement terms.

What generic entry risks exist for a testosterone gel covered by this patent?

The principal generic entry risk is formulation substitution. A generic applicant can develop a testosterone gel that maintains transdermal delivery while avoiding at least one required feature of claim 1.

High-value design-around variables

Variable	Potential design-around
Permeation enhancer	Replace oxacyclohexadecan-2-one with another enhancer
Alcohol system	Use a different alcohol concentration or solvent architecture
Co-solvents	Omit glycerin or substitute a different co-solvent
Thickener	Use a rheology modifier outside the claimed concentration
Viscosity	Formulate below 2,000 cps or above 6,000 cps
pH	Use a pH outside the claimed 4-8 range
Dosage form	Use a patch, spray, lotion, or another delivery system
Dosing method	Use a regimen that does not meet the claimed AUC limitation

A generic applicant does not need to reproduce the branded formulation if it can establish pharmaceutical equivalence, therapeutic equivalence, and adequate product performance through the applicable FDA pathway.

The claim’s method-of-use format may also reduce its reach against a product whose approved labeling does not direct treatment of hypogonadism in the claimed manner. That defense depends on the labeling, promotional conduct, and evidence of induced infringement.

Does US 7,608,606 create biosimilar risk?

No. Testosterone is a small-molecule active ingredient, and topical testosterone gels are generally addressed through the abbreviated new drug application pathway rather than the biosimilar pathway under the Public Health Service Act.

The relevant competitive risk is generic, not biosimilar. The principal regulatory questions concern pharmaceutical equivalence, bioequivalence, topical product performance, dosage uniformity, clinical pharmacology, and therapeutic equivalence.

How strong is the patent estate for testosterone gel products?

The estate was strongest when several protections operated together:

A formulation patent covering the enhancer and solvent system.
Related patents covering composition or delivery methods.
FDA listing and Hatch-Waxman litigation rights.
Product-specific clinical and manufacturing know-how.
Commercial physician and patient familiarity.

US 7,608,606 alone has a narrower practical scope than a composition-of-matter patent. It does not cover all testosterone gels, all transdermal testosterone products, or testosterone as an active ingredient. Its value depends on whether a competing product uses the claimed enhancer and falls within the claimed formulation ranges.

Patent-strength assessment

Factor	Assessment
Claim type	Method claims with detailed formulation limitations
Breadth	Moderate within a defined formulation combination
Design-around difficulty	Moderate to low
Dependence on testing	High for viscosity, composition, and AUC limitations
Active-ingredient protection	None for testosterone itself
Current blocking value	Limited after expiration
Historical commercial value	Material for products using the claimed formulation architecture
Biosimilar relevance	None
Generic relevance	High during the active patent term

What patent litigation and settlements affected the market?

Testosterone-gel patent disputes generally centered on Paragraph IV certifications, infringement claims, patent validity, and the timing of generic approval. Settlement agreements in this market can include delayed generic entry, authorized-generic arrangements, licenses, supply provisions, and restrictions on launch.

The public record for any particular settlement must be reviewed against the relevant district-court docket, FDA patent listing, and applicable antitrust disclosures. A patent settlement does not necessarily establish claim validity. Its business effect depends on the agreed launch date and whether the agreement includes an authorized generic or other entry mechanism.

How does US 7,608,606 compare with other testosterone products?

Product category	Typical protection focus	Relationship to US 7,608,606
Testim-type gel	Lactone-enhanced topical gel formulation	Closest technical relationship
AndroGel-type gel	Separate formulation, delivery, and labeling patents	Competing estate, not automatically covered
Fortesta-type gel	Different concentration and administration profile	Potentially outside the claimed formulation architecture
Axiron-type topical solution	Axillary delivery and solution formulation	Generally distinct dosage form and use profile
Testosterone patches	Adhesive and membrane-controlled delivery	Outside topical-gel limitations
Injectable testosterone	Depot formulation and injection regimen	Outside transdermal method claims
Oral testosterone products	Oral absorption and hepatic-exposure technology	Outside the claimed route

The patent is therefore most relevant to a testosterone gel that reproduces the specified enhancer-solvent-thickener system, not to the broader testosterone replacement market.

What geographic coverage does the patent provide?

US 7,608,606 provides rights only in the United States. Foreign counterparts, if any, require separate analysis based on national filings, grant status, maintenance fees, and expiration dates.

A U.S. patent cannot block manufacture, sale, or use entirely outside the United States unless another jurisdiction has a corresponding enforceable patent. U.S. importation and commercial distribution can still create U.S. infringement exposure under 35 U.S.C. § 271.

Manufacturing outside the United States does not automatically eliminate risk. Importing a product that practices the claimed method or is made through a patented process can present separate issues under U.S. patent law.

Key Takeaways

US 7,608,606 covers a method of treating male hypogonadism with a specific testosterone topical gel.
The most important limitation is the required oxacyclohexadecan-2-one permeation enhancer.
The claim also requires defined ranges for testosterone, alcohol, thickener, pH, and viscosity.
Claims 2 through 8 add dose, AUC, polyethylene glycol, and narrower enhancer limitations.
The patent is associated with Testim-type testosterone gel technology and related formulation patents.
It does not cover testosterone generally or every transdermal testosterone product.
The patent’s ordinary U.S. term ended in the 2023-2024 period.
Current generic risk is driven more by expired patent barriers, later patents, FDA requirements, and formulation design-around strategy than by US 7,608,606 alone.
Testosterone products face generic, not biosimilar, competition.
Any current freedom-to-operate conclusion must account for the full patent family, Orange Book listings, terminal disclaimers, patent-term adjustment, and litigation record.

FAQs

Can a testosterone gel infringe US 7,608,606 if it does not contain pentadecalactone?

Literal infringement of claim 1 is unlikely because the claim expressly requires oxacyclohexadecan-2-one. Equivalence theories could still be raised, but they would depend on the technical and prosecution history record.

Does claim 1 cover a testosterone gel with 10% testosterone?

Yes, claim 1 permits testosterone from about 0.1% to about 5% by weight. A 10% formulation would fall outside that stated range, subject to the legal interpretation of “about.”

Is US 7,608,606 a composition patent or a method patent?

It is principally a method patent. The claims require transdermal administration to a male for treatment of hypogonadism and do not merely claim the gel as an article independent of use.

Can a generic applicant avoid claims 2 and 6 by omitting pharmacokinetic data?

Avoiding pharmacokinetic testing does not itself avoid the claims. The issue is whether the administered product actually satisfies the claimed AUC increase. Regulatory data may nevertheless become relevant evidence in an infringement dispute.

Does patent expiration permit immediate sale of any testosterone gel?

No. Expiration removes the patent exclusion created by US 7,608,606, but FDA approval, controlled-substance requirements where applicable, labeling, manufacturing compliance, other patents, and regulatory exclusivity remain separate legal requirements.

References

United States Patent and Trademark Office. (n.d.). Patent term adjustment and patent term calculation guidance. https://www.uspto.gov
U.S. Food and Drug Administration. (n.d.). Drugs@FDA: Testim, NDA 021902. https://www.accessdata.fda.gov
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book. https://www.fda.gov
U.S. Code. (n.d.). 21 U.S.C. § 355 and 35 U.S.C. § 271(e): Abbreviated new drug applications and patent certification procedures. https://uscode.house.gov
United States Patent and Trademark Office. (2009). US Patent No. 7,608,606, methods and compositions for transdermal delivery of testosterone. https://patents.google.com/patent/US7608606B2
United States Patent and Trademark Office. (2002). US Patent No. 6,818,226, testosterone gel composition. https://patents.google.com/patent/US6818226B2

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Argentina	039644	⤷ Start Trial
Argentina	087484	⤷ Start Trial
Austria	371456	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 7,608,606

Summary for Patent: 7,608,606