US Patent 6,335,031: Scope, Claim Positioning, and US Landscape

US Patent 6,335,031 claims a stabilization-and-formulation package for (S)-N-ethyl-3-{(1-dimethylamino)ethyl}-N-methyl-phenyl-carbamate (“Compound A”), paired with low-level antioxidants and applied to pharmaceutical compositions and transdermal device architectures. The dominant claim theme is not new molecular entity activity; it is use of defined antioxidant classes and defined ranges to prevent degradation of Compound A in a polymer matrix / device system, including backing/liner/adhesive stack configurations.

Because the claim set is highly specific to (i) Compound A identity/form, (ii) antioxidant identity and concentration windows, and (iii) transdermal construction elements, the enforceable scope is concentrated on transdermal or polymer-matrix formulations where Compound A stability is addressed through the enumerated antioxidant choices and loading levels.

What does US 6,335,031 actually claim?

1) Core claim: pharmaceutical composition with antioxidant + carrier

Claim 1 defines a pharmaceutical composition comprising:

(a) a therapeutically effective amount of Compound A in free base or acid addition salt form
(b) about 0.01 to 0.5 wt% antioxidant (based on total composition weight)
(c) a diluent or carrier

This claim anchors broad “composition” coverage, but only in so far as the antioxidant is present in the defined low range and is part of a composition containing Compound A.

2) Concentration-dependent composition claim

Claim 2 adds a quantitative payload:

Compound A: 1 to 40 wt%

This narrows Claim 1 by requiring Compound A loading in a mid-range suitable for formulations that remain processable and releasable.

3) Antioxidant definition: enumerated species and sub-sets

Claim 3 lists antioxidant options:

tocopherol and esters
ascorbic acid
BHT (butylhydroxytoluene)
butylhydroxyanisole (BHA)
propyl gallate

Claim 4 narrows Claim 3 to:

α-tocopherol or ascorbyl palmitate

Claim 5 hard-codes:

α-tocopherol = 0.1 wt%

This creates a high-certainty, narrow “commercial target” within the broader 0.01 to 0.5 wt% band.

4) Device-oriented polymer matrix composition with fixed ranges

Claim 6 is the most technically constrained polymer-matrix composition claim:

Compound A (free base form): 20 to 40 wt%
polymethacrylate: 10 to 30 wt%
acrylate copolymer: 40 to 60 wt%
α-tocopherol: 0.05 to 0.3 wt%
total = 100%

This is not a generic antioxidant claim. It is a matrix recipe: specific polymer families, specific relative weight bands, and a specific antioxidant selection with a narrower antioxidant loading window than Claim 1.

5) Transdermal devices: support/substrate/adhesive/liner architecture

Claim 7: transdermal device comprising a pharmaceutical composition as in Claim 1, supported by a substrate.

Claim 8: composition located between an adhesive layer and substrate.

Claim 9: release liner contacts the adhesive layer.

These three claims push coverage toward end-to-end transdermal patch constructions, not just standalone drug formulations.

6) Device-dependent stabilization additives: silicone oil

Claim 10: pharmaceutical composition of Claim 1 further comprises silicone oil.

Claim 11 is the most structurally explicit device claim:

backing layer
a layer with a therapeutically effective amount of Compound A and an amount of antioxidant effective to stabilize Compound A from degradation in a polymer matrix
release liner
discrete adhesive layer disposed between the Compound-A/polymer matrix layer and the release liner for releasably fixing to skin

Claim 12 expands the adhesive layer to include silicone oil.

Claim 13-14 repeat antioxidant subsets for device claims:

Claim 13: antioxidants as in Claim 3
Claim 14: antioxidants as in Claim 4

7) Method claim: stabilization by combining drug + antioxidant

Claim 15: method of stabilizing Compound A, comprising:

forming a composition by combining Compound A (free base or acid addition salt) with an amount of antioxidant effective to stabilize from degradation.

Claims 16-19 specify the antioxidant identities and loading constraints:

Claim 16: antioxidants as in Claim 3
Claim 17: α-tocopherol or ascorbyl palmitate
Claim 18: antioxidant 0.01 to 0.5 wt%
Claim 19: α-tocopherol = 0.1 wt%

Claim 20 adds silicone oil to the method composition.

What is the effective enforceable scope (and where are the pressure points)?

A) The “gating element” is Compound A identity and form

Every independent or dependent pathway uses Compound A as the stabilized moiety:

free base or acid addition salt for several claims (1, 7, 11, 15)
free base specifically in Claim 6 (20 to 40 wt% plus polymer recipe)

Practical implication: Design-around can occur by changing the drug form (salt vs free base) only if it meaningfully avoids the narrow “free base” conditions in Claim 6, while still being within broader claims that accept salt forms.

B) The enforceable antioxidant window is tight

Claim 1 sets 0.01 to 0.5 wt% antioxidant.

That window matters because it is not unlimited “stabilizer” space. Claims 4-5-18-19 and 6 further constrain loading:

α-tocopherol specifically:
- Claim 4/14: identity constraint (no range)
- Claim 5/19: 0.1 wt%
- Claim 6: 0.05 to 0.3 wt%
α-tocopherol esters or ascorbyl palmitate:
- Claims 4 and 14 allow α-tocopherol or ascorbyl palmitate (identity set)
- Claims 17 and 18 allow method use at 0.01 to 0.5 wt%

Pressure point for infringement risk:

If a competitor uses the same antioxidant identities but outside the range, it may avoid some claims (at least the range-anchored ones).
If a competitor uses a non-enumerated antioxidant, it likely avoids identity-based dependent claims (3/4/13/14/16/17), but may still face exposure under Claim 1 if their antioxidant still fits the claimed antioxidant universe (it does not if it is truly outside).

C) Claim 6 and Claim 11 define “device ecosystem” coverage

The most monetizable enforceable scope tends to arise where patents claim:

the exact matrix blend (Claim 6)
the exact device stack (Claim 11)

Claim 11 includes the adhesive + release liner positioning, which is often stable across commercial transdermal patches. This makes Claim 11 a strong hook for transdermal commercialization where the patch is built with discrete layers and a liner/adhesive arrangement.

D) Silicone oil is a secondary but operationally relevant modifier

Silicone oil appears in:

Claim 10 (composition)
Claim 11/12 (device/adhesive layer)
Claim 20 (method)

The silicone oil element can become a check-box risk factor if a competitor’s formulation uses silicone oils in either the drug matrix system or the adhesive layer. Even when silicone oil is not present, Claim 1/7/8/9/11 (depending on interpretation) may still be asserted, because silicone oil is not required in the baseline Claim 1 transdermal device pathway.

E) Salt vs free base: avoidable but not sufficient alone

Because multiple claims accept “free base or acid addition salt,” changing to an acid addition salt is not a universal design-around. It is most useful against the most constrained free base language in Claim 6, which ties to the matrix recipe.

How does the claim set map to product forms and business scenarios?

Products most exposed

Transdermal patches using:
- Compound A (free base or acid addition salt, depending on claim)
- antioxidant from the enumerated list (especially α-tocopherol)
- antioxidant loading within 0.01-0.5 wt% and sometimes tighter bands
- polymer matrix with polymethacrylate and acrylate copolymer (if pursuing Claim 6 alignment)
- device layers consistent with Claim 11 (backing + drug/polymer layer + release liner + discrete adhesive layer)
Commercially realistic α-tocopherol formulations:
- α-tocopherol at 0.1 wt% triggers Claims 5 and 19 (composition and method).
- α-tocopherol between 0.05 and 0.3 wt% and a matching polymer matrix triggers Claim 6.

Lower-risk zones (relative)

Antioxidants outside the enumerated set:
- If the stabilizer is not in (tocopherol/esters, ascorbic acid, BHT, BHA, propyl gallate, α-tocopherol, ascorbyl palmitate), dependent claims (3/4/13/14/16/17) fall away.
Antioxidant loading outside 0.01-0.5 wt%:
- Claims 1 and 18 are range-gated.
- Claims anchored at 0.1 wt% (5/19) are more sensitive to the exact loading.
Non-transdermal delivery:
- The transdermal device claims (7-14) may not apply.
- Pharmaceutical composition claims (1-6) and method claims (15-20) can still apply if the same stabilization principle is used in compositions.

What is the likely patent landscape structure around this US patent (enforcement strategy view)?

This patent is best understood as a formulation-stabilization patent rather than a chemical synthesis patent or broad use patent. Landscape effects generally cluster into four buckets:

1) “Primary molecule” patents (upstream)

Typically cover:

Compound A preparation
pharmacological uses
polymorphs or salts

US 6,335,031 is not claiming activity endpoints. It claims stabilization in pharmaceutical formulations and transdermal device systems.

2) “Stabilizer/enhancer formulation” patents (adjacent)

US 6,335,031 competes with other patents that try to lock down:

alternative antioxidants
alternative concentration ranges
alternative stabilizer combinations
different polymer matrices or film formers

Within this bucket, US 6,335,031 is narrow in antioxidant identity but broad in “effective amount” language (Claims 1 and 15 use “effective to stabilize from degradation” style language, yet still cap range via Claim 1/18).

3) “Transdermal architecture” patents (device stack)

Other patents often claim:

adhesives, liners, backing materials
layer placement
permeation control layers
silicone oil or other surface agents

US 6,335,031 is device-structured in Claims 7-9 and 11-12, but it is still anchored to the presence of Compound A and specific antioxidant classes/loadings.

4) “Matrix recipe” patents (composition in specific polymers)

Claim 6 is the “recipe lock”:

polymethacrylate and acrylate copolymer bands
Compound A free base in 20-40%
α-tocopherol in 0.05-0.3%

Competitors usually attack these by:

changing the polymer family ratio bands
replacing polymethacrylate or acrylate copolymer with different polymer families
using different antioxidants outside the enumerated list or outside the range

Where do claims 1-20 sit relative to one another (scope hierarchy)?

Claim	Coverage type	Key constraints that narrow scope
1	Pharmaceutical composition	Compound A + antioxidant at 0.01-0.5 wt% + diluent/carrier
2	Pharmaceutical composition	adds Compound A 1-40 wt%
3	Composition (dependent)	antioxidant must be in enumerated list
4	Composition (dependent)	antioxidant must be α-tocopherol or ascorbyl palmitate
5	Composition (dependent)	α-tocopherol fixed at 0.1 wt%
6	Composition (dependent)	free base form + specific polymer bands + α-tocopherol 0.05-0.3 wt%
7	Transdermal device	composition of claim 1 supported on substrate
8	Transdermal device	composition between adhesive layer and substrate
9	Transdermal device	release liner contacts adhesive layer
10	Composition (dependent)	silicone oil added
11	Transdermal device	backing + drug/polymer layer + release liner + discrete adhesive layer arrangement
12	Transdermal device	adhesive layer includes silicone oil
13	Transdermal device (dependent)	antioxidant must match enumerated list
14	Transdermal device (dependent)	antioxidant must be α-tocopherol or ascorbyl palmitate
15	Method	combine Compound A with antioxidant effective to stabilize
16	Method (dependent)	antioxidant must match enumerated list
17	Method (dependent)	antioxidant must be α-tocopherol or ascorbyl palmitate
18	Method (dependent)	antioxidant 0.01-0.5 wt%
19	Method (dependent)	α-tocopherol 0.1 wt%
20	Method (dependent)	silicone oil added

This hierarchy shows two “claim engines”:

Range + identity engine (Claims 1-5, 13-14, 18-19)
Recipe + architecture engine (Claims 6, 11-12)

Investment and R&D implications: how to read this patent in diligence

If you are assessing a candidate transdermal program containing Compound A

Risk centers on:

antioxidant identity selection (α-tocopherol and/or ascorbyl palmitate are repeatedly claimed)
antioxidant loading (0.01-0.5 wt% and especially 0.1 wt% and 0.05-0.3 wt%)
polymer matrix recipe alignment (Claim 6: polymethacrylate 10-30% and acrylate copolymer 40-60% with Compound A free base 20-40%)
device stack consistency with backing + liner + discrete adhesive layer (Claim 11)

If you are licensing or challenging validity/enforceability

Strategic focus typically lands on:

whether competitors used antioxidant concentrations outside the claimed windows
whether they use alternative stabilizers outside the enumerated lists
whether the device stack deviates from the discrete adhesive layer placement defined in Claim 11
whether the competitor’s Compound A is in the free base vs salt form that matters to Claim 6

Key Takeaways

US 6,335,031 is a formulation and transdermal stabilization patent for Compound A, not a broad method of use or synthesis patent.
The enforceable core is Compound A + enumerated antioxidant(s) at 0.01-0.5 wt% in a pharmaceutical composition and embedded in transdermal device architectures.
The highest specificity risk points are α-tocopherol at 0.1 wt% (Claims 5 and 19) and the Claim 6 matrix recipe (polymethacrylate + acrylate copolymer + Compound A free base + α-tocopherol 0.05-0.3 wt%).
Transdermal exposure strengthens through device stack claims (Claims 7-9 and 11-12) that require discrete adhesive and liner arrangements.
Silicone oil is a meaningful additive in multiple claims but is not the only gate to coverage; antioxidant selection and loading remain the main gates.

FAQs

1) Does the patent require the antioxidant to be one of the listed species?

Yes. Claim 1 requires “an antioxidant,” and dependent claims specify the enumerated list. The most enforceable dependent hooks are Claims 3, 4, 13, 14, 16, and 17.

2) Is α-tocopherol singled out as a special case?

Yes. Claims 4 and 5 lock α-tocopherol as either the antioxidant identity and at 0.1 wt% for Claim 5. Claim 6 also uses α-tocopherol at 0.05 to 0.3 wt%.

3) Are salt forms covered?

Many claims include Compound A in free base or acid addition salt form. Claim 6 is narrower and requires free base form.

4) Is this patent only about transdermal delivery?

No. It includes pharmaceutical composition claims (1-6) and method of stabilizing claims (15-20), alongside transdermal device claims (7-14).

5) Which claims are most likely to map to a commercial transdermal patch formulation?

Claim 11 for device stack plus Claims 7-9 for device structure, with Claim 6 providing the tightest polymer recipe hook where the matrix uses specified polymer bands and α-tocopherol loading.

References

[1] US Patent 6,335,031.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Germany	9800526	Jan 12, 1998

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	223711	⤷ Start Trial
Australia	2278599	⤷ Start Trial
Australia	745661	⤷ Start Trial
Brazil	9906920	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Summary for Patent: 6,335,031