Scope, Claims, and US Patent Landscape for Drug US6133251
US 6,133,251 claims a biphasic-to-multistage oral contraception regimen built around (i) natural estrogen exposure in a first and third stage, (ii) a two-group second stage where estrogen stays constant but gestogen content increases in the second group, and (iii) an additional placebo stage. The independent claim structure ties the count of daily dosage portions per stage and the relative gestogen amount between second-stage subgroups to both product and method forms.
What matters commercially and legally is the claim’s tight numeric architecture (2 to 4; 3 to 5; 13 to 17; 2 to 4) combined with specific estrogen classes (estradiol, conjugated equine estradiol, estradiol compounds metabolized to estradiol) and gestogen constraints (natural or synthetic gestogens; with dependents specifying a defined gestogen panel including dienogest).
What is the core claim scope in US 6,133,251?
Independent claim theme (product + method)
Claims 1 and 4 (product) and claims 5 and 7 (method) share the same regimen logic:
- First stage: 2 to 4 daily dosage portions, each has an effective amount of at least one natural estrogen.
- Second stage: split into two groups:
- First second-stage group: 3 to 5 dosage portions of estrogen + gestogen.
- Second second-stage group: 13 to 17 dosage portions of estrogen + gestogen.
- Key relationship: the second group contains more gestogen than the first group.
- Third stage: 2 to 4 daily dosage portions of natural estrogen only.
- Key relationship: estrogen amount is constant in first and third stages, but the third-stage estrogen amount is smaller than first-stage (as written).
- Additional stage: 2 to 4 daily placebo portions.
This is a structured, multi-stage daily dosing schedule with explicit stage lengths and explicit gestogen step-up across the two second-stage subgroups.
Primary compositional constraints (independent claims)
Independent product claim 1 includes:
- Estrogen selection: estradiol, conjugated equine estradiol, or estradiol-compounds metabolized to estradiol when taken.
- Gestogen presence: “at least one natural or synthetic gestogen” in second stage only.
- Estrogen constancy language: estrogen is “constant” in first and third stages but third-stage estrogen is smaller than first-stage. This is internally inconsistent as drafted, but it remains a literal requirement that would be litigated based on claim construction.
Independent product claim 4 refines selection:
- Estrogen limited to: estradiol, conjugated equine estradiol, estradiol valerate
- Gestogens limited to: progesterone, desogestrel, gestoden, levonorgestrel, medroxyprogesterone acetate, chlormadinone acetate, dienogest
Method claims track dosing steps
Claims 5 and 7 mirror the product claims but framed as sequential administration:
- Step a): 2 to 4 estrogen-only first stage portions
- Step b): 3 to 5 first second-group portions (estrogen + gestogen)
- Step c): 13 to 17 second second-group portions (estrogen + gestogen; higher gestogen than group b)
- Step d): 2 to 4 third stage estrogen-only portions
- Step e): 2 to 4 additional placebo portions
Claim 5 repeats the estrogen class restriction (estradiol, CEE, estradiol-compounds metabolized to estradiol). Claim 7 adds the narrowed estrogen and gestogen enumerations.
How do dependent claims narrow the scope?
Claim 2 (product)
- Adds a numeric relationship:
gestogen amount in second group = 1.5 to 3 times the gestogen amount in the first group (within the second stage).
- This increases enforceability against products that only slightly increase gestogen.
Claim 3 (product)
- Locks: gestogen = dienogest and estrogen = estradiol.
Claim 6 (method)
- Locks: gestogen = dienogest and estrogen = estradiol for the method.
Claim 7 (method, expanded enumerations)
- Narrows estrogen to: estradiol, conjugated equine estradiol, estradiol valerate
- Narrows gestogens to a defined list including dienogest.
What schedule architecture does the claim cover (and what it excludes)?
Schedule coverage
The independent claims require the following minimum-and-maximum daily portion counts:
- First stage: 2 to 4 portions
- Second stage total: (3 to 5) + (13 to 17) = 16 to 22 portions
- Third stage: 2 to 4 portions
- Additional placebo stage: 2 to 4 portions
So the total cycle length is first + second + third + placebo:
- Minimum: 2 + 16 + 2 + 2 = 22 portions
- Maximum: 4 + 22 + 4 + 4 = 34 portions
This claim is therefore not a generic “21/7” scheme; it covers longer and variable-length cycles with a gestogen step-up within the long estrogen+gestogen run.
What is structurally excluded
A regimen would fall outside the claim if it fails any of the following literal elements:
- No two-group second stage with different gestogen amounts.
- Gestogen present in first/third stages or absent in the second stage.
- Stage lengths outside the bounded ranges (e.g., a 21 active day scheme without matching stage partitions).
- Estrogen not in the claimed “natural estrogen” category (or not selected from the independent enumerations, depending on which claim is asserted).
- Placebo stage not present or not within 2 to 4 daily portions.
Claim charts in plain terms (what must be proven)
For independent product claim 1
A claimant must show a contraception combination preparation with:
- A labeled or implied cycle unit having four sequential stages with the claimed daily portion counts.
- First stage: estrogen-only portions (2 to 4).
- Second stage: two groups of estrogen+gestogen portions (3 to 5, then 13 to 17).
- Gestogen step-up: second group contains more gestogen than first second-stage group.
- Third stage: estrogen-only portions (2 to 4).
- Additional placebo stage: placebo portions (2 to 4).
- Estrogen identity: estradiol/CEE/estradiol-compound-to-estradiol class.
Dependent claims add quantitative and identity refinements:
- Claim 2 requires the step-up to be 1.5 to 3x.
- Claims 3 and 6 require estradiol + dienogest.
- Claim 4 and 7 require the specific estrogen and gestogen enumeration lists.
For method claims (5 and 7)
The proving elements track the steps:
- administering the same stage-wise portions in the same order
- matching the same numeric stage counts and gestogen step-up
Patent landscape: likely claim positioning versus existing contraceptive patents
How US 6,133,251 fits within the typical contraceptive patent ecosystem
Contraception patent families often split along:
- Formulation claims (which hormones, dosages)
- Regimen claims (how dosing is sequenced and for how many days)
- Manufacturing/process claims (tablet structures, coatings, etc.)
- Use claims (methods of contraception)
US 6,133,251 is predominantly a regimen architecture patent: it is defined by stage duration and within-cycle hormone composition changes. That shifts enforceability toward proving labeling, instructions, and therapeutic administration.
Key landscape risks for competitors
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Regimen step-up specificity
- Claim 2 makes the gestogen step-up numeric (1.5 to 3x). Competitors using a smaller ramp can argue they do not meet that limitation.
-
Dienogest + estradiol lock-in
- Claims 3 and 6 strongly narrow to estradiol + dienogest, which is a high-value infringement target because dienogest is used in certain modern regimens.
-
Estrogen identity narrowing
- Claims 4 and 7 narrow estrogen to an enumerated set including estradiol valerate and CEE.
-
Stage length bounded
- Many marketed regimens are fixed to 21/7 or 24/4 or 28-day patterns. This patent accommodates 22 to 34 days and requires the multi-stage partitioning, which can exclude conventional cycles even when hormones are similar.
Key landscape opportunities for design-arounds
To avoid literal coverage:
- change stage counts outside 2 to 4, 3 to 5, or 13 to 17 bounds
- eliminate the two-group gestogen step-up inside the long second stage
- change the estrogen identity away from the claimed natural estrogen classes (or away from the enumerated sets of dependent claims)
- use a gestogen not covered by the dependent lists (still may be covered under independent “natural or synthetic gestogen” language in claim 1, so this must be evaluated by which claim is asserted)
Infringement exposure map (by claim type)
High exposure
- Estradiol-based multi-stage oral contraceptives where gestogen increases mid-cycle inside the long active second stage.
- Products that use dienogest with estradiol in a schedule that matches the four-stage structure and counts.
Moderate exposure
- Regimens meeting the stage partitioning but with gestogen step-up outside 1.5 to 3x (limiting exposure to independent claim 1/5 depending on hormone identity and regimen compliance).
Lower exposure
- Conventional fixed cycles (especially those with uniform active dosing) that do not create the required two-group second stage with different gestogen levels.
How to read the claim architecture for landscape diligence
Stage counting is the anchor
The claim is engineered around how many pills are in each stage. Landscape diligence should therefore compare:
- total cycle length
- the partition point between first active estrogen and the two-group active estrogen+gestogen period
- the partition between second-group active dosing and estrogen-only third stage
- the placebo length at the end
Gestogen step-up is the second anchor
The claim is not satisfied by gestogen presence alone. It requires:
- more gestogen in the second group than the first group
- and in dependent claim 2, a constrained ratio range (1.5x to 3x)
Identity constraints are claim-dependent
- Independent claim 1 is broader on gestogen identity (any natural or synthetic gestogen) but bounded on estrogen class.
- Dependent claims 3 and 6 are narrow (dienogest + estradiol).
- Dependent claim 4 and 7 provide hard lists of gestogens and estradiol subclasses.
Key Takeaways
- US 6,133,251 claims a stage-based oral contraception regimen: estrogen-only (2 to 4), then estrogen+gestogen with two gestogen levels (3 to 5 then 13 to 17), then estrogen-only (2 to 4), then placebo (2 to 4).
- The core legally operative feature is a gestogen step-up within the second stage, with dependent claim 2 requiring a 1.5 to 3x ratio.
- The highest-value enforceability point is the narrow estradiol + dienogest combination in claims 3 and 6 (product and method).
- A meaningful portion of competitive regimens may avoid literal coverage by missing the two-group second stage architecture, falling outside the stage count bounds, or using a hormone sequencing pattern that does not produce the required within-cycle change.
FAQs
1) Is US 6,133,251 a formulation patent or a regimen patent?
It is a regimen architecture patent, defined by stage counts, stage order, and the within-cycle gestogen amount change across two second-stage groups.
2) What single limitation most drives infringement risk?
The combination that matches the four-stage dosing schedule with a two-group second stage where the second group has higher gestogen (and dependent claim 2 sets a numeric ratio).
3) Which claims are the most narrow and commercially targeted?
Claims 3 and 6: estradiol + dienogest.
4) Can a competitor avoid coverage by changing the gestogen ratio slightly?
If the ratio misses the dependent range in claim 2 (1.5x to 3x), that limits claim 2 but may still leave exposure under independent claims if the “more gestogen” relationship and stage structure are met.
5) Does the patent require placebo days?
Yes. It requires an additional placebo stage of 2 to 4 daily placebo portions.
References
- US Patent 6,133,251. “Combination preparation for contraception” (claims provided in user prompt).
