Scope and claims of US Patent 7,608,607: testosterone transdermal gel viscosity/pH/solvent/oxacyclohexadecan-2-one controlled-release concentration methods

US 7,608,607 claims a narrow method-of-use and formulation-linked transdermal dosing regime for achieving a defined testosterone exposure in men with hypogonadism. The claim set is anchored to (i) a topical testosterone gel composition with specific ranges for testosterone, the solubilizer/penetration-related excipient oxacyclohexadecan-2-one, viscosity, and pH; (ii) a defined solvent system (high ethanol or isopropanol plus propylene glycol and glycerin co-solvents) with optional polyethylene glycol (PEG) as a crystallization inhibitor; and (iii) pharmacokinetic performance quantified by an AUC0-24 increase versus no-dose control after a single unit-dose application. In practical freedom-to-operate terms, the estate is strongest against testosterone transdermal gels that replicate the particular excipient package (oxacyclohexadecan-2-one + the ethanol/isopropanol/propylene glycol/glycerin mixture) and hit the same exposure targets under single-application unit-dose conditions.

US Patent 7,608,607 claims scope: what exactly is protected?

Short answer: The patent protects a method for maintaining therapeutically effective testosterone serum concentration in a male with hypogonadism by transdermally delivering a testosterone topical gel with a specific composition envelope (testosterone, oxacyclohexadecan-2-one, thickener, solvent system, optional PEG), plus performance KPIs (AUC0-24 increase after a single unit dose) and product-parameter constraints (viscosity and pH, dosing amount).

Claim 1 (core independent claim) breaks into three protection pillars

Patient condition and target: treating hypogonadism by maintaining therapeutically effective serum testosterone concentration.
Delivery format and operational parameters:
- transdermal topical gel applied to the skin
- viscosity about 500 to 20,000 cP
- pH about 3 to 9
- unit dose containing ~1 to 300 mg testosterone
- dosing schedule is effectively “single application” for PK measurement.
Composition composition ranges (must all be met):
- A. Testosterone: about 0.1 to 5 wt%
- B. Oxacyclohexadecan-2-one: about 0.5 to 15 wt%
- C. Thickening agent: about 0.1 to 10 wt%
- D. Solvent mixture includes:
  - about 60 to 75 wt% ethanol or isopropanol
  - plus co-solvents propylene glycol and glycerin

Claim 2–3 (PEG crystallization inhibitor narrowing)

Claim 2 adds polyethylene glycol (PEG) to the composition.
Claim 3 limits PEG to 0.001 to 5 wt%.

This creates a second, more specific sub-family within the method space: the “PEG present in the specified band” variant.

Claim 4 (thickener range refinement)

Thickening agent limited to 1 to 6 wt% (subset of Claim 1’s 0.1 to 10 wt%).

Claim 5 (pharmacokinetic performance KPI)

Claim 5 is the most restrictive because it couples the formulation and unit dose to a quantified outcome:

After a single application of the unit dose to the skin,
the serum exposure AUC0-24 is increased by about 100 to 35,000 ng·dL greater than no-dose control in the same 24-hour window.

This is a performance-limiting claim. Even where excipients fall within the ranges, an accused gel must also be capable of producing the specified exposure delta under the claimed dosing conditions to infringe Claim 5-dependent coverage.

Claims 6–9 (viscosity bands refinement)

Claim 6: viscosity 1,000 to 9,000 cP
Claim 7: 2,000 to 8,000 cP
Claim 8: 3,000 to 7,000 cP
Claim 9: pH 4 to 8 (subset of 3 to 9)

These dependent claims carve “narrow corridor” product parameter bins that are often the basis for design-around and regulatory bridging.

Claim 10 (PEG-containing independent claim)

Claim 10 is a second independent claim that is effectively Claim 1 plus PEG crystallization inhibitor:

composition includes:
- testosterone, oxacyclohexadecan-2-one, thickener
- solvent system (60–75 wt% ethanol or isopropanol + propylene glycol + glycerin)
- PEG: 0.001 to 5 wt%
and it retains the same transdermal unit-dose and AUC0-24 performance delta language as Claim 5.

Claims 11–15 (dependent refinement of Claim 10)

11: viscosity 1,000–9,000 cP
12: viscosity 2,000–8,000 cP
13: viscosity 3,000–7,000 cP
14: pH 4–8
15: thickener 1–6 wt%

Practical inference: “must satisfy all limitations”

Because the independent claim is structured as a method that requires delivery of a composition “which comprises” all those components in those ranges, an accused product that misses any element (e.g., does not include oxacyclohexadecan-2-one in the specified range, or uses a different solvent system not meeting the 60–75 wt% ethanol/isopropanol band, or has a viscosity/pH outside the claimed windows) does not read on the claim as written.

Which product attributes most constrain infringement risk for US 7,608,607?

Short answer: The highest-risk attributes are the combination of oxacyclohexadecan-2-one at 0.5–15 wt% with a high-alcohol solvent system (60–75 wt% ethanol/isopropanol) plus propylene glycol and glycerin, and then the ability to show AUC0-24 increase after a single unit dose consistent with the KPI range.

Highest-leverage claim elements

Oxacyclohexadecan-2-one (0.5–15 wt%)
- If a competing gel uses a different solubilizer/penetration enhancer and does not include oxacyclohexadecan-2-one in-range, that is a direct design-around against independent claims.
Solvent system specificity
- 60–75 wt% ethanol or isopropanol is a large fraction, but it is still a precise constraint. Many gels are ethanol-lean or use different co-solvent packages.
- Co-solvents are required: propylene glycol and glycerin.
Viscosity and pH corridor
- Viscosity 500–20,000 cP is broad, but dependent claims tighten it.
- pH 3–9 is broad; dependent claims tighten to 4–8.
Unit-dose application and PK metric
- Claim 5/10’s AUC0-24 delta is a performance limitation.
- This can create evidentiary complexity in enforcement and in patentability invalidation arguments, but it still narrows the method to products that produce the specified exposure outcome.

Where infringers often survive or avoid exposure

Use of a similar overall “testosterone transdermal gel” platform is not enough. The claim requires a matching excipients + operational parameters + single-dose PK profile.
Alternative solvent systems that do not meet the ethanol/isopropanol 60–75 wt% band plus propylene glycol and glycerin may avoid claim coverage even if overall viscosity and pH are adjusted.

What are the key claim “ranges” and what do they mean for design-around?

Short answer: The patent is built as a series of numerical guardrails. Changing excipient identity or pushing one parameter outside the band can break literal infringement.

Composition and parameter map (from the claims)

Element	Claim language band
Testosterone	0.1 to 5 wt%
Oxacyclohexadecan-2-one	0.5 to 15 wt%
Thickening agent	0.1 to 10 wt% (and 1 to 6 wt% in dependent claims)
Viscosity	500 to 20,000 cP (and narrower 1,000–9,000; 2,000–8,000; 3,000–7,000)
pH	3 to 9 (and narrower 4–8)
Ethanol or isopropanol	60 to 75 wt%
Co-solvents	propylene glycol + glycerin
PEG (crystallization inhibitor)	0.001 to 5 wt% (Claims 2/3 and independent Claim 10 and dependents)
Testosterone unit dose	1 to 300 mg testosterone
PK KPI	AUC0-24 increase of 100 to 35,000 ng·dL vs no-dose control

Design-around levers in practice

Remove oxacyclohexadecan-2-one or move it out of 0.5–15 wt%.
Alter solvent composition so ethanol/isopropanol is not 60–75 wt% or remove one co-solvent (propylene glycol or glycerin).
Shift pH outside 4–8 (to defeat dependent claim coverage) or outside 3–9 (to defeat independent Claim 1/10).
Shift viscosity outside dependent corridors (or outside 500–20,000 cP).
Change dosing/PK outcome such that the AUC0-24 delta does not fall in 100–35,000 ng·dL.

How does the AUC0-24 requirement affect enforcement and invalidity risk?

Short answer: The AUC0-24 “greater than no-dose” performance band converts an otherwise typical formulation claim into a formulation-plus-performance claim, narrowing the factual scope in litigation and increasing the role of pharmacokinetic evidence.

Why AUC-based limits matter

They tether infringement to measurable exposure outcomes after a single unit-dose application.
They can complicate “paper infringement” arguments based solely on ingredient ranges.
They can also be used to attack enablement or anticipation if prior art does not disclose or support the claimed PK delta under comparable dosing, skin conditions, and measurement methodology.

How this interfaces with claim dependencies

Claims 1 and 10 require composition and delivery; Claims 5 and the corresponding language in Claim 10 require the AUC0-24 delta.
Even if the composition matches, an accused product can try to argue that its in-human exposure does not meet the KPI band.

What does the dependent claim structure suggest about the patent’s prosecution strategy?

Short answer: The claims show a classic layered approach: broad independent coverage on excipient package and dosing format, then tighter corridors on PEG presence, viscosity, pH, thickener loading, and then a performance KPI tied to AUC0-24.

Likely strategic reading

The patent is positioned to capture multiple commercial products:
- non-PEG versions (Claim 1 family)
- PEG crystallization inhibitor versions (Claim 10 family)
- products tuned to specific viscosity and pH windows used in gel stability and spreadability
The AUC0-24 clause suggests the applicant used formulation and clinical PK results to justify patentability and/or to distinguish prior art.

US 7,608,607 patent landscape: how many competing testosterone transdermal gel pathways can it hit?

Short answer: On claim text alone, infringement is limited to gels that match the excipient and solvent architecture, not just testosterone transdermal delivery broadly.

“Hit” categories (most aligned to claim language)

Testosterone transdermal gels with:
- oxacyclohexadecan-2-one in a mid-to-high wt% band
- ethanol or isopropanol as the dominant solvent fraction at 60–75 wt%
- propylene glycol and glycerin co-solvents
- viscosity and pH within the claimed corridors
- and unit-dose application achieving an AUC0-24 delta in the specified band

“Likely miss” categories

Gels that use different penetrants/solubilizers (no oxacyclohexadecan-2-one).
Ethanol-poor formulations or formulations where ethanol/isopropanol is not 60–75 wt%.
Solvent systems that do not include both propylene glycol and glycerin.
Products that tune viscosity/pH outside the claimed windows.
Units that do not produce the AUC0-24 delta after single application as claimed.

What formulations are protected: gel-only, testosterone topical, unit dose, and hypogonadism?

Short answer: The claims are explicitly limited to a testosterone topical gel composition applied to male skin for hypogonadism treatment, measured via AUC0-24 after a single unit dose.

Notably excluded by claim language

Patch delivery systems are not covered as written.
Injection, pellets, implants, and other non-topical transdermal formats are not covered.
Oral, buccal, nasal, or intranasal are not covered.
Non-hypogonadal indications are not covered.

Key takeaways

US 7,608,607 protects a transdermal testosterone gel method combining strict composition ranges (testosterone, oxacyclohexadecan-2-one, thickener, solvent system) with strict product parameters (viscosity and pH) and a single-dose PK exposure KPI (AUC0-24 increase of 100 to 35,000 ng·dL).
The patent’s practical infringement risk is concentrated in products that reproduce the oxacyclohexadecan-2-one + 60–75 wt% ethanol/isopropanol + propylene glycol and glycerin architecture.
Dependent claims narrow additional corridors for PEG presence, viscosity sub-ranges, pH sub-ranges, thickener band, and the AUC performance requirement.
Design-around is most credible by changing the excipient package or solvent system so that at least one of the independent-claim limitations is not met.

FAQs

1) Does US 7,608,607 cover any testosterone transdermal gel?
No. Coverage is limited to gels that match the claim’s specific composition ranges, viscosity/pH constraints, and (for the KPI-dependent language) AUC0-24 performance after a single unit dose.

2) What is the role of oxacyclohexadecan-2-one in the claims?
It is a required composition component in the independent claims, constrained to about 0.5 to 15 wt%. Removing it or moving outside that range breaks literal coverage.

3) Is polyethylene glycol optional or required?
PEG is optional in Claim 1/and dependent claim sets that do not add PEG. It becomes required in Claim 10 and Claims 2–3/and corresponding dependents that recite PEG as a crystallization inhibitor.

4) How do viscosity and pH affect claim scope?
Broad independent windows exist (viscosity 500–20,000 cP; pH 3–9). Dependent claims narrow these corridors (viscosity up to 3,000–7,000 cP; pH 4–8).

5) Can a product infringe if it matches ingredients but not AUC0-24?
For claim coverage that includes the AUC0-24 KPI language (notably Claim 5 and the independent Claim 10’s KPI portion), matching ingredients alone is insufficient if the measured AUC0-24 delta is outside the stated band.

References

US Patent 7,608,607.

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: 7,608,607

Summary for Patent: 7,608,607