United States Patent 7,163,931: Scope, Claim Architecture, and US Landscape for an Estrogen-Cyclodextrin Plus Drospirenone Formulation
What is the protected invention in US 7,163,931?
US 7,163,931 claims methods of inhibiting ovulation (Claim 1) and methods of hormone replacement therapy (Claim 27) in a female using a specific composition:
- Component (i): a complex between an estrogen and a cyclodextrin
- Component (ii): drospirenone
- Component (iii): one or more excipients
- Key functional limitation: the composition has stability such that the estrogen remains at specified levels after 12 months at 40°C and 75% RH
The core stability threshold is:
- At least 85% w/w of the estrogen remaining vs. initial content after 12 months at 40°C and 75% RH (Claims 1 and 27)
- A dependent escalation to:
- At least 90% w/w after the same stress test (Claims 26 and 52)
The remaining dependent claims narrow the invention by specifying:
- whether the estrogen/cyclodextrin complex is a granulate and limits its relative humidity (≤60%)
- the identity of estrogen and cyclodextrin (often pegged to ethinyl estradiol and β-cyclodextrin)
- quantitative ranges for estrogen content, drospirenone content, and estrogen-to-cyclodextrin molar ratios
- excipient constraints, notably PVP (polyvinylpyrrolidone) maximums or “essentially free”
- physical attributes such as micronization
- particle size for granulated material
- optional antioxidant inclusion
How broad is Claim 1’s method scope?
Claim 1 is the principal claim. It is a method-of-using claim, not a composition claim, but the method is defined by administering a composition with defined composition elements and stability performance.
Claim 1 (method for inhibiting ovulation) elements:
1) A composition comprising:
- estrogen–cyclodextrin complex
- drospirenone
- one or more excipients
2) A stability requirement:
- estrogen amount is ≥85% w/w of initial after 12 months at 40°C and 75% RH
Practical implication: many generic “use drospirenone + an estrogen + a cyclodextrin complex” products will fall outside the claim unless they meet the specific accelerated stability acceptance criteria.
What does the claim set cover functionally (ovulation inhibition vs HRT)?
The claims cover two related indications framed as methods of use:
| Claim cluster |
Target method |
Triggering condition |
Composition boundary |
| Claims 1-26 |
Inhibiting ovulation |
administering the defined composition |
stability ≥85% (Claim 1) or ≥90% (Claim 26), plus dependencies |
| Claims 27-52 |
Hormone replacement therapy |
administering the defined composition |
stability ≥85% (Claim 27) or ≥90% (Claim 52), plus dependencies |
Key structural point: Claim 27 repeats Claim 1’s architecture for HRT. The functional distinction (ovulation inhibition vs HRT) is the major change; the formulation constraints are otherwise substantially aligned.
What are the main narrowing axes in dependent claims?
The dependent claims define specific embodiments along several axes:
1) Stability performance thresholds
- ≥85% w/w estrogen remaining after 12 months at 40°C / 75% RH: Claims 1, 27
- ≥90% w/w estrogen remaining after 12 months at 40°C / 75% RH: Claims 26, 52
These two thresholds matter because they define a performance staircase. If a competitor’s formulation degrades below 90% but still above 85%, it may still infringe the 85%-based claims but not the higher-threshold dependent claims.
2) Granulate preparation and controlled humidity
- Complex is a granulate preparation with:
- relative humidity ≤60% measured at 20°C to 40°C (Claims 2, 28)
- Granulated preparation mean particle size ≥100 μm (Claims 25, 51)
This ties claim scope to specific solid-state processing and intermediate material handling parameters.
3) Estrogen identity and amount
Estrogen is defined broadly in Claim 17, then narrowed repeatedly to ethinyl estradiol:
- Estrogen list (Claim 17):
- ethinyl estradiol
- estradiol
- estradiol sulfamates
- estradiol valerate
- estradiol benzoate
- estrone
- estrone sulfate
- mixtures
Then:
- Estrogen is ethinyl estradiol (Claims 18, 44)
- Quantitative ranges for estrogen as % w/w of total composition:
- 0.002% to 2% (Claims 3, 29)
- 0.002% to 2% (Claims 4, 30) (duplicate style, same range)
- 0.004% to 0.2% (Claims 5, 31)
Plus relative constraints tied to the complex:
- With ethinyl estradiol + β-cyclodextrin:
- ethinyl estradiol in the complex is 5% to 20% w/w relative to the complex (Claims 6, 32)
- alternatively 8% to 15% w/w relative to the complex (Claims 7, 33)
4) Cyclodextrin identity
Cyclodextrin is broadly defined, then pinned to β-cyclodextrin:
- Cyclodextrin list (Claim 19):
- α-, β-, γ-cyclodextrin
- alkylated or acylated derivatives
Then:
- Cyclodextrin is β-cyclodextrin or alkylated/acylated derivative (Claims 20, 46)
5) Estrogen-to-cyclodextrin molar ratio
- molar ratio 2:1 to 1:10 (Claims 21, 47)
This is a key formulation parameter that can be attacked for non-coverage if a product’s stoichiometry falls outside the window.
6) Drospirenone level and physical form
Drospirenone content:
- 0.4% to 20% w/w (Claims 8, 34)
- 0.8% to 10% w/w (Claims 9, 35)
- 1.5% to 5% w/w (Claims 10, 36)
Drospirenone form:
- micronized drospirenone (Claim 22; no explicit HRT parallel claim, but Claim 48 in HRT cluster covers micronization of drospirenone).
7) Excipients: PVP limits and “essentially free”
PVP is treated as a controlled excipient:
- PVP at most:
- 2% w/w (Claims 11, 37)
- 1% w/w (Claims 12, 38)
- 0.5% w/w (Claims 13, 39)
- 0.2% w/w (Claims 14, 40)
- Composition essentially free of PVP (Claims 15, 41)
Other allowed excipients (Claim 16 and Claim 42):
- starch, cellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, maltodextrin
8) Processing of the complex: micronization + optional antioxidants
- Complex micronized (Claims 23, 49)
- Optional antioxidant (Claims 24, 50)
9) Micronization and particle size
- Drospirenone micronized (Claims 22, 48)
- Complex micronized (Claims 23, 49)
- Granulate mean particle size ≥100 μm (Claims 25, 51)
These parameters define physical form, which can be engineered around, but only if the resulting product still meets the other formulation and stability requirements.
What is the “core claim nucleus” competitors must match to read on?
The practical infringement nucleus is:
1) A composition including drospirenone and an estrogen–cyclodextrin complex
2) Administering the composition for:
- inhibiting ovulation or
- hormone replacement therapy
3) Stability: estrogen remaining at:
- ≥85% after 12 months at 40°C / 75% RH (base claims)
- optionally ≥90% (dependent claims)
Everything else is narrowing.
What are the strongest defensible features (what to expect as design-arounds)?
Given the claim set, the highest-leverage design-arounds for a non-infringing product are:
- Fail stability limits: formulation that does not maintain estrogen at the 85% or 90% thresholds under the exact stress test
- Change solid-state processing: avoid granulate / humidity-controlled granulate states required by Claims 2/28 and avoid particle size limitations
- PVP strategy: if a product uses PVP >0.2% w/w, it can fall outside multiple dependent claims that constrain PVP. But base Claim 1 does not contain a PVP maximum, so this only limits coverage if the competitor is still within the Claim 1 stability and composition structure.
- Cyclodextrin identity: substitute cyclodextrin types outside the claimed list or use non-cyclodextrin inclusion systems.
- Stoichiometry: move estrogen:cyclodextrin molar ratio outside 2:1 to 1:10.
- Avoid micronization dependencies: if those dependent claims matter for a specific litigation theory, a product can avoid them (but Claim 1 still may apply).
How does the claim architecture affect freedom-to-operate (FTO) analysis?
The set is largely a “formula meets stability” bundle expressed as method-of-use. For FTO:
- A product that matches the general inclusion architecture (estrogen–cyclodextrin complex + drospirenone) but fails stability acceptance may avoid the base claim.
- A product that matches stability and inclusion architecture can still try to avoid depending on:
- estrogen dose ranges,
- PVP limits,
- micronization/particle size,
- granulate relative humidity.
- But since the broadest coverage does not require the dependent features, stability and inclusion architecture remain the highest-risk matching points.
What is the US patent landscape likely to look like around this claim set?
The claim language points to a formulation family around:
- estrogen inclusion complexes with cyclodextrins
- drospirenone combination
- stability under 40°C / 75% RH
- solid-state (granulation, humidity control, micronization)
- controlled excipient profiles (notably PVP)
In practice, US landscapes for this kind of claim set tend to cluster into three types of patents:
1) Inclusion-complex patents (estrogen + cyclodextrin) focusing on improved stability or bioavailability
2) Combination product patents adding drospirenone and addressing formulation compatibility and degradation
3) Manufacturing process and solid-state patents specifying granulation, moisture, particle size, and drying/micronization approaches
Intersections most relevant to US 7,163,931:
- if a later patent changes cyclodextrin species, stoichiometry, or excipient system, it can still create an alternative pathway if stability is not matched to the 85%/90% thresholds
- if a later patent improves stability using different inclusion chemistry or a different protective excipient system, it can coexist if it avoids the claimed combination structure and/or test performance
What would a competitor’s non-infringing product typically do under this framework?
A generic or innovator designing around US 7,163,931 would typically pick one of these strategies:
- Use drospirenone with estrogen but not via the claimed estrogen–cyclodextrin complex, or use a cyclodextrin system outside the listed categories.
- Keep the complex but ensure the accelerated stability result is below the claimed threshold, so the product does not meet the “≥85%” or “≥90%” criteria at 40°C / 75% RH for 12 months.
- Use the correct complex but alter:
- estrogen concentration,
- drospirenone concentration,
- PVP presence,
- granulate humidity,
- particle size,
- micronization state,
to route away from dependent claims while assessing whether base claim coverage still exists.
Key claim-by-claim scope map (invention coverage terms)
Below is a condensed claim map showing what each major dependent branch adds.
| Dependent claim(s) |
Adds/limits |
Where it bites |
| 2, 28 |
complex is a granulate with RH ≤60% at 20°C–40°C |
manufacturing/solid-state |
| 3-5, 29-31 |
estrogen % w/w ranges |
dose envelope |
| 6-7, 32-33 |
ethinyl estradiol amount relative to EtE-β-CD complex |
complex composition |
| 8-10, 34-36 |
drospirenone % w/w ranges |
dose envelope |
| 11-15, 37-41 |
PVP max limits and “essentially free” |
excipient envelope |
| 16, 42 |
excipients list |
formulation support |
| 17, 43 |
estrogen identity list |
API scope |
| 18, 44 |
ethinyl estradiol-only |
API scope |
| 19-20, 45-46 |
cyclodextrin identity list; β-CD focus |
excipient complex |
| 21, 47 |
estrogen:cyclodextrin molar ratio 2:1 to 1:10 |
stoichiometry |
| 22-23, 48-49 |
micronized drospirenone; micronized complex |
physical form |
| 24-25, 50-51 |
antioxidant; particle size ≥100 μm for granulate |
solid-state and stability adjunct |
| 26, 52 |
stability raised to ≥90% |
performance |
What are the litigation-relevant takeaways from the claim set?
- The claim’s “hard wall” is the accelerated stability requirement. It is the most objective and testable limitation.
- The rest is parameterized ranges (dose, stoichiometry, PVP limits, particle size, humidity), which are easier to adjust but may still leave base coverage if the inclusion architecture and stability are met.
- PVP limits are only a dependent-claim constraint. A composition that uses PVP >0.2% could still infringe Claim 1 if stability and the core complex + drospirenone structure are met.
Key Takeaways
- US 7,163,931 protects method-of-use coverage for inhibiting ovulation and for hormone replacement therapy using a drospirenone + estrogen–cyclodextrin complex composition with defined accelerated stability.
- The dominant risk factor is performance: ≥85% estrogen remaining after 12 months at 40°C/75% RH (base) and ≥90% (dependent).
- Dependent claims add layered constraints on granulation humidity, particle size, estrogen and cyclodextrin identity, estrogen dose and stoichiometry, drospirenone dose, PVP excipient caps, and micronization/antioxidant.
- A credible design-around targets either (a) the claimed complex architecture, or (b) the stability test outcome, with secondary attention to dependent parameter ranges.
FAQs
1) Does Claim 1 require PVP to be absent or limited?
No. PVP limitations appear only in dependent claims (Claims 11-15 and 37-41). Claim 1 only requires the composition to contain the estrogen–cyclodextrin complex, drospirenone, excipients, and to meet the stability criterion.
2) Which parameter is the most objective for enforcement: composition identity or stability?
Stability. Claims 1 and 27 require ≥85% w/w estrogen remaining after 12 months at 40°C and 75% RH; Claims 26 and 52 require ≥90%.
3) Is the method coverage limited to ethinyl estradiol and β-cyclodextrin?
No. That combination is a dependent narrowing set (Claims 6-7, 32-33; β-CD in Claims 20 and 46, and ethinyl estradiol in Claims 18 and 44). Claim 1 includes broader estrogen and cyclodextrin categories.
4) Can a product fall outside the dependent claims but still infringe Claim 1?
Yes. Dependent claim features (PVP limits, RH ≤60% granulate, micronization, particle size, specific dose ranges) narrow coverage, but Claim 1 can still be asserted if its core requirements are met.
5) What is the maximum estrogen:cyclodextrin molar ratio permitted by the claim set?
The range in dependent claims is 2:1 to 1:10 (Claims 21 and 47).
References
[1] United States Patent 7,163,931.
