United States Patent 7,608,608: Scope, Claim Architecture, and US Landscape

US Patent 7,608,608 claims a testosterone transdermal gel delivery method with a defined viscosity and pH window and a specific “macrocyclic enhancer” package to sustain therapeutic testosterone exposure. The independent claim is a method claim directed to maintaining a therapeutically effective blood-serum testosterone concentration in males for treating hypogonadism via transdermal delivery using a topical gel with constrained formulation parameters. Dependent claims narrow by adding a crystallization inhibitor, by defining unit-dose and exposure (AUC) performance criteria, and by enumerating specific macrocyclic enhancers.

What is claimed at the core?

Claim 1 is the operative scope. It requires all of the following, as a coupled set:

Method purpose and patient population
- A method for maintaining therapeutically effective concentration of testosterone in blood serum of a male for treating hypogonadism.
Route and form
- Transdermal delivery by applying to skin a topical gel.
- Gel physical attributes:
  - Viscosity: about 2000 to about 6000 cps
  - pH: about 4 to about 8
Formulation composition constraints
- Testosterone: about 0.1 to about 5 wt. %
- Macrocyclic enhancer: about 0.5 to about 25 wt. %, selected from:
  - 3-methylcyclopentadecanone
  - 9-cycloheptadecen-1-one
  - cyclohexadecanone
  - cyclopentadecanone
  - oxacyclohexadecan-2-one
  - and mixtures thereof
- Thickening agent: about 1 to about 6 wt. %
- Solvent system: mixture includes
  - about 60 to about 75 wt. % ethanol or isopropanol, plus
  - propylene glycol and glycerin as co-solvents

The claim is not a generic testosterone gel claim. It is a tight parameter bundle: patient + purpose + transdermal gel + viscosity/pH + testosterone %, enhancer %, thickener %, and a solvent/co-solvent system.

How broad is Claim 1 versus Claim 2 and performance limitations?

Claim 1 (independent): breadth anchored by formulation parameter ranges

The effective infringement/validity risk under Claim 1 depends on whether the accused product or process matches the bundle:

Route/form: transdermal gel applied to skin (not patch, not oral, not injectable).
Therapeutic target: maintains therapeutic serum testosterone concentration for hypogonadism.
Gel properties: viscosity 2000-6000 cps and pH 4-8.
Composition (must all be met):
- Testosterone: 0.1-5 wt. %
- Macrocyclic enhancer: 0.5-25 wt. %
- Thickener: 1-6 wt. %
- Solvents: 60-75 wt. % ethanol or isopropanol + propylene glycol + glycerin.

Practical scope takeaway: even if a competitor uses a macrocyclic enhancer of the same family, they can avoid Claim 1 by moving out of at least one required parameter zone (viscosity, pH, enhancer wt. %, testosterone wt. %, thickener wt. %, or solvent/co-solvent architecture).

Claim 2 (dependent): crystallization inhibitor add-on

Claim 2 expands Claim 1 by requiring:

About 0.001 to about 5 wt. % polyethylene glycol as a crystallization inhibitor.

Scope effect: Claim 2 is narrower than Claim 1, but it matters for competitors that use PEG in gels. PEG use becomes a potential “lock-in” feature that can increase overlap with the dependent claim.

Claim 3 (dependent): unit dose and AUC0-24 performance metric

Claim 3 imposes a performance and dosing structure on Claim 1:

Composition is maintained on skin for time sufficient for delivery.
Applied as a unit dose containing:
- about 1 to about 300 mg testosterone
After a single application, the resulting exposure is constrained by a comparative AUC criterion:
- AUC0-24 increase is about 100 to about 35,000 ng·h/dL greater than the AUC0-24 without the dose.

Scope effect: This claim can be a leverage point in enforcement and licensing because it ties formulation and dosing to a measurable pharmacokinetic outcome. Competitors may be able to design around by altering dose form, dosing regimen, or formulation parameters that move their AUC0-24 increment outside the window.

How are macrocyclic enhancers used to define claim boundaries (Claims 4-8)?

Claims 4-8 carve out specific members of the enhancer list from Claim 1:

Claim 4: enhancer is 3-methylcyclopentadecanone
Claim 5: enhancer is 9-cycloheptadecen-1-one
Claim 6: enhancer is cyclohexadecanone
Claim 7: enhancer is cyclopentadecanone
Claim 8: enhancer is oxacyclohexadecan-2-one

Scope effect: These claims are narrower than Claim 1 but can be easier to map in an invalidity or freedom-to-operate assessment when a competitor discloses (or is proven to use) one of the specified enhancers at qualifying wt. % within the full Claim 1 structure.

Claim chart style mapping (what must be present for infringement)

Claim element	Required limitation	Design-around lever
Route / dosage form	Transdermal delivery via topical gel applied to skin	Use non-gel form (if outside claim’s route/form) or different delivery platform
Patient / therapeutic context	Male with hypogonadism; maintains therapeutically effective serum testosterone	Indication switch alone does not eliminate composition/form requirements, but could matter for method framing
Gel physical parameters	Viscosity 2000-6000 cps; pH 4-8	Shift viscosity or pH out of ranges
Testosterone content	0.1-5 wt. %	Shift testosterone wt. % out of range
Enhancer identity	Macrocyclic enhancer must be from listed set	Use a different enhancer type not in list
Enhancer loading	0.5-25 wt. %	Shift enhancer wt. % out of range
Thickener	1-6 wt. %	Use a thickener level outside range
Solvents	60-75 wt. % ethanol or isopropanol + propylene glycol + glycerin	Change solvent percentage or remove/replace required co-solvents
Claim 2 add-on	PEG crystallization inhibitor 0.001-5 wt. %	Use no PEG or outside range
Claim 3 add-on	1-300 mg testosterone per unit dose; single-application AUC0-24 increment 100-35,000 ng·h/dL	Adjust unit dose, dosing time, or formulation to move AUC increment

What is the practical “claim scope geometry” for market products?

The macrocyclic enhancer constraint is the primary specificity axis

Claim 1 requires a macrocyclic enhancer from a defined list and at defined loading. If a competing gel uses different chemical classes of enhancers (common approaches in testosterone gels include general permeation enhancers, fatty acid derivatives, terpenes, or other well-known penetration promoters), it can fall outside this patent even if other elements overlap.

Gel physical parameters add a “formulation tweak” boundary

Even if a product uses one of the listed enhancers, it can avoid Claim 1 by shifting:

viscosity outside 2000-6000 cps, or
pH outside 4-8.

This is a meaningful design-around lever because viscosity and pH are formulation controllables.

Solvent system constrains “solvent swap” strategies

Claim 1 is not satisfied by “alcohol plus something.” It requires:

60-75 wt. % ethanol or isopropanol, plus
propylene glycol and glycerin as co-solvents.

A competitor that changes alcohol type (ethanol vs isopropanol) must still match the wt. % and retain the propylene glycol + glycerin co-solvent system.

Claim 3 can convert formulation overlap into exposure overlap

If a competitor matches the formulation constraints, Claim 3 adds a dosing and pharmacokinetic outcome window. That can be a second gate for infringement and also a testable point for litigation or licensing.

Patent landscape: how this claim set typically positions against US testosterone transdermals

Where this patent likely sits conceptually

US 7,608,608 is positioned at the intersection of:

transdermal testosterone gel delivery, and
permeability enhancement using a defined “macrocyclic enhancer” class,
with performance anchored by AUC0-24 increment (Claim 3).

In the broader US testosterone transdermal patent space, companies typically pursue protection on one or more of:

enhancer chemistry and loading,
gel rheology and pH windows,
solvent systems and cosolvents,
dosing unit formats and dosing regimens,
and PK exposure targets.

This patent’s novelty emphasis is reflected by how narrowly the enhancer list is defined and how tightly the formulation parameters are coupled.

How to assess likely overlap pathways in practice

For freedom-to-operate (FTO) mapping, the most predictive queries are:

Does the competitor’s gel use one of the listed macrocyclic enhancers?
If no, Claim 1 is less likely to read.
If yes, does it use the enhancer at 0.5-25 wt. % and testosterone at 0.1-5 wt. %?
This controls whether the enhancer is not only present but present at the claimed concentration ranges.
Does the formulation meet viscosity and pH constraints?
Even with matching chemistries, rebalancing rheology or buffering can move out of claim territory.
Does the solvent system match the alcohol and co-solvents?
Removing glycerin or changing propylene glycol usage can be decisive.
Is PEG present as a crystallization inhibitor in Claim 2 range?
If competitor uses PEG generally for formulation, Claim 2 becomes relevant.
Does dosing strategy and resulting AUC0-24 increment align with Claim 3 window?
This is where formulation similarity may not equal legal risk if the exposure outcome is shifted.

Enforcement and licensing signals from the claim set

Claim 1 enables broad method coverage but needs full parameter match

Because Claim 1 includes a complete formulation parameter bundle, enforcement often benefits from:

discovery of the exact formulation composition,
gel specification testing (viscosity and pH),
and solvent percentage confirmation.

Claim 3 provides measurable traction

AUC0-24 comparative increase (“greater than without dose”) supports:

objective pharmacokinetic comparison,
bench-to-in vivo mapping,
and potential use of clinical/PK study readouts.

Dependent claims create multiple “fallback” claim targets

Claims 2 and 3 allow the patent owner to pursue narrower theories if:

the competitor avoids the base bundle but uses PEG in the specified range, or
the competitor matches base formulation but not the broad method framing without the unit-dose/AUC performance constraints.

Key Takeaways

US 7,608,608 Claim 1 is a testosterone hypogonadism treatment method via transdermal topical gel with specific gel viscosity (2000-6000 cps), pH (4-8), formulation wt. % ranges, and a defined enhancer list. All limitations must be present together.
The macrocyclic enhancer list is the primary boundary: Claim 1 requires one of five specific macrocyclic enhancers (or mixtures) at 0.5-25 wt. %.
Design-around is feasible by moving out of parameter windows (viscosity, pH, testosterone %, enhancer loading, thickener %, alcohol % or co-solvents, or eliminating required co-solvents).
Claim 2 adds a secondary hook: PEG 0.001-5 wt. % as a crystallization inhibitor.
Claim 3 adds a dosing and PK exposure gate: 1-300 mg testosterone per unit dose and AUC0-24 increment 100-35,000 ng·h/dL after a single application.

FAQs

1) What is the single most important limitation for determining coverage under US 7,608,608?

Macrocyclic enhancer identity and loading: the gel must include a listed macrocyclic enhancer at 0.5-25 wt. % within the full Claim 1 formulation and property windows.

2) Does using a testosterone transdermal gel automatically risk infringement?

No. Risk requires matching the coupled Claim 1 bundle, including viscosity 2000-6000 cps, pH 4-8, defined wt. % ranges, and the specific enhancer + solvent/co-solvent system.

3) How does Claim 3 change the enforcement picture?

Claim 3 adds an objective exposure and dosing constraint: a single unit dose with 1-300 mg testosterone must produce an AUC0-24 increase of 100-35,000 ng·h/dL compared with no dose.

4) What is the main design-around if a competitor wants to keep similar rheology?

Adjust at least one coupled parameter out of bounds (commonly pH, viscosity, enhancer loading, or solvent/co-solvent architecture) so the full Claim 1 bundle fails.

5) Where does PEG matter?

PEG becomes relevant under Claim 2 only if used as a crystallization inhibitor in the 0.001-5 wt. % range within the Claim 1 composition.

References

[1] US Patent 7,608,608, “Method for maintaining a therapeutically effective concentration of testosterone,” claims 1-8.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Argentina	039644	⤷ Start Trial
Argentina	087484	⤷ Start Trial
Austria	371456	⤷ Start Trial
Australia	2003228612	⤷ Start Trial
Brazil	0309390	⤷ Start Trial
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Details for Patent: 7,608,608

Summary for Patent: 7,608,608