United States Patent 6,911,461: What Is Claimed, Where the Scope Lands, and How the Landscape Looks
What does US 6,911,461 claim at a functional level?
US 6,911,461 is a composition-and-method patent built around a narrow stereochemical definition of a single small-molecule scaffold: (2S)-2-[2-oxy-4-propylpyrrolidinyl]butanamide and its specified (4R) and (4S) diastereoisomers, plus salts. Claim 2 adds formulation. Claim 3 adds a broad multi-indication therapeutic use umbrella. Claim 4 narrows to selected conditions. Claim 5 narrows to one specific diastereomer.
Claim set (as provided)
| Claim |
Category |
Core scope element |
| 1 |
Product |
(4R) and (4S) diastereoisomers of (2S)-2-[2-oxy-4-propylpyrrolidinyl]butanamide or salts |
| 2 |
Composition |
Pharmaceutical composition with diluent/carrier |
| 3 |
Method of treatment |
Administering a therapeutic dose for a long list of CNS, pain, cardiopulmonary, and other indications |
| 4 |
Method narrowing |
Condition is epilepsy, neuropathic pain, bipolar disorder, or migraine |
| 5 |
Product (sub-scope) |
(2S)-2-[(4R)-2-oxo-4-propylpyrrolidinyl]butanamide or salts |
Key structural takeaway: Claim 1 is broad within a tight chemical frame because it covers both diastereoisomers at the 4-position while fixing the (2S) center. Claim 5 is narrower and pins the 4R diastereomer while further describing a 2-oxo variant in the pyrrolidinyl moiety, suggesting the patent family’s claims are sensitive to exact functional group identity (oxy vs oxo) and stereochemical assignment.
Where is the claim scope broadest versus narrowest?
The scope breadth is driven by three levers: (i) stereochemistry, (ii) structural definition of the amide/pyrrolidine substituent and oxidation state, and (iii) indication language.
1) Stereochemistry: broad chemical coverage in Claim 1
- Claim 1 covers two diastereoisomers: (4R) and (4S), but only with (2S) configuration at the butanamide carbon bearing the pyrrolidinyl substituent.
- That means a competitor can design around by changing:
- the (2S) configuration to (2R), or
- removing the ability to fall under the exact stereochemical description (for example, by using a different stereochemical relationship or mixture not meeting the specific diastereomer definition, depending on how the patent is construed in prosecution and enforcement).
2) Functional-group/structural specificity: Claim 1 vs Claim 5 signals fine-grained boundary
- Claim 1 uses “2-oxy-4-propylpyrrolidinyl” language.
- Claim 5 uses “2-oxo-4-propylpyrrolidinyl” language.
- That is not stylistic; it changes the chemical description of the ring substituent (oxy vs oxo), which can:
- tighten the scope for Claim 5 relative to Claim 1, or
- create interpretive questions during enforcement about whether Claim 5 is a subset, a correction, or a separate variant.
Practical impact: In freedom-to-operate terms, any candidate product must be evaluated against both claim paths, because the patent includes both a general stereochemical claim and a narrower diastereomer claim with different ring functional group wording.
3) Indication: Claim 3 is the widest use claim
Claim 3 lists a long set of therapeutic areas, including:
- Epilepsy / epileptogenesis / seizure disorders / convulsions
- Bipolar disorders / mania / depression / anxiety
- Migraine
- Neuralgia / chronic pain / neuropathic pain
- Cerebral ischemia
- Cardiac arrhythmia
- Myotonia / cocaine abuse
- Stroke / myoclonus / essential tremor
- Neonatal cerebral haemorrhage
- Amyotrophic lateral sclerosis / spasticity
- Parkinson’s disease
- Bronchial asthma / asthmatic status / allergic bronchitis
- Asthmatic syndrome / bronchial hyperreactivity / bronchospastic syndromes
- Allergic and vasomotor rhinitis / rhinoconjunctivitis
Claim 4 narrows the “condition” subset to:
- epilepsy, neuropathic pain, bipolar disorder, or migraine
Practical impact: If a generic or licensee targets any of the listed conditions with a therapeutically effective dose of the compound of Claim 1, Claim 3 can be implicated even if the label uses only one indication. Claim 4 provides narrower fallback coverage, typically easier to read onto specific clinical programs.
How courts and examiners typically construe this kind of claim
What matters in claim construction for product-by-stereochemistry and salts?
In US patent practice, these claims usually turn on:
- Whether a product contains the claimed stereochemical configuration (not merely similar pharmacology).
- Whether the product is within the described compound family, including whether a proposed salt is “pharmaceutically acceptable” and covered as a variant of the same base.
- Whether functional group wording differences (oxy vs oxo) are treated as distinct structures or as consistent drafting of the same chemical entity.
Because Claim 1 is limited to (2S) and includes both (4R) and (4S), enforcement typically focuses on stereochemical proof and analytical chemistry (chirality, diastereomer ratios, and confirmatory characterization).
How indication breadth affects enforcement
Broad method claims are enforced as:
- “use” claims based on the therapeutic dose being administered for a listed condition.
- If clinical development or marketing includes any of the conditions in Claim 3, the method claim creates a higher litigation footprint for competitors than a narrower indication patent would.
Landscape analysis: where competitors are likely to be blocked or to carve out
What design-arounds are most plausible against Claims 1 and 5?
For a competitor targeting the same pharmacological space, the highest-value carve-outs are:
- Stereochemical change at the (2) center
- Claim 1 is restricted to (2S).
- Changing to (2R) (single enantiomer) is the cleanest conceptual boundary.
- Diastereomer strategy and mixture control
- Claim 1 covers both 4R and 4S diastereoisomers, so merely avoiding one diastereomer does not help if the formulation contains the other.
- Ring functional-group boundary (oxy vs oxo)
- Claim 1 and Claim 5 use different descriptors for the pyrrolidinyl functionality.
- A candidate structure that is truly different at that position can potentially avoid literal infringement depending on claim interpretation.
- Claim 5-specific boundary (4R only)
- Even if Claim 1 is avoided, Claim 5 could still be a target if the compound lands on the 4R diastereomer with the particular “2-oxo” description.
What does Claim 2 add operationally?
Claim 2 is a straightforward formulation claim:
- If the active ingredient falls under Claim 1, standard formulation with pharmaceutically acceptable diluents/carriers is likely covered.
- This reduces the ability to avoid infringement using formulation-only changes (unless the competitor uses a different active structure that falls outside Claim 1).
What does Claim 3 add operationally?
Claim 3 is the main enforcement lever across therapeutic programs because it is tied to:
- administering a therapeutic dose of the compound of Claim 1
- to treat a condition selected from a long list
For market entrants, this shifts risk from “compound-only” to “product + indication + dose.”
Patent landscape mapping around a stereochemical platform (how to think about filings)
How the claims typically position within a broader patent family
A US patent that claims both:
- stereochemically defined products (Claims 1 and 5),
- formulations (Claim 2),
- and broad use (Claims 3 and 4)
is usually anchored to earlier work that establishes:
- the synthetic route and stereochemical assignment of the key intermediate(s),
- the biological activity across multiple CNS and related indications,
- and the therapeutic dosing regimen language used for method claims.
In practice, such families often generate:
- continuation patents with narrower stereochemical or salt definitions,
- jurisdictional counterparts (EP, WO, JP, CN) with matching but sometimes tightened language,
- and later patents directed to specific formulations, dosing regimens, or biomarkers.
Where 6,911,461 likely sits relative to generic entry pressure
Without the rest of the bibliographic record (priority, filing dates, assignee, and expiration/terminal disclaimer status), the only defensible landscape inference from the claim text alone is:
- the patent is a core chemical-use patent rather than a purely late-stage formulation or method-of-manufacture patent.
- that tends to create longer practical leverage for the holder against generic substitution for the covered indication set, because use and composition claims attach even if the formulation changes.
Actionable “scope checklist” for FTO or competitive assessment
Does a candidate product fall within Claim 1?
A candidate must be tested against:
- Stereochemistry at (2): must be (2S).
- Diastereomer coverage at (4): must be either 4R or 4S (Claim 1 covers both).
- Core scaffold: must match the described 2-[2-oxy-4-propylpyrrolidinyl]butanamide mapping.
- Salt forms: must be pharmaceutically acceptable salts of the same compound.
If it does, what else triggers risk?
- Claim 2: whether the marketed product is formulated with conventional diluents/carriers.
- Claim 3: whether the marketed dosing is for any listed condition (even one).
- Claim 4: whether the product targets epilepsy, neuropathic pain, bipolar disorder, or migraine.
Key Takeaways
- US 6,911,461 is stereochemically bounded: Claim 1 fixes (2S) and includes both 4R and 4S diastereoisomers, so “diastereomer avoidance” is not a reliable carve-out.
- Use coverage is broad in Claim 3: it spans major CNS indications (epilepsy, bipolar, migraine, pain and neuropathic pain) plus cardiopulmonary indications (asthma and related syndromes) and additional neurological conditions.
- Claim 2 is a conventional formulation layer: if Claim 1 is met, standard carrier/diluent formulations typically land within Claim 2.
- Claim 5 narrows to a single diastereomer with different functional-group wording: the “2-oxo” versus “2-oxy” language signals that structural exactness matters for design-around.
- Competitive risk assessment should start with structure-activity mapping to the stereochemical and functional group descriptors, then test indication alignment against Claim 3’s list.
FAQs
1) Is the patent limited to a single diastereomer?
No. Claim 1 covers both (4R) and (4S) diastereoisomers with (2S) configuration. Claim 5 is narrower and specifies the (4R) diastereomer.
2) Does Claim 3 require multiple indications to be treated?
No. Claim 3 lists indications; coverage is triggered by administering a therapeutic dose for any condition within the listed set.
3) Can a competitor avoid infringement by changing formulation ingredients only?
Not if the active ingredient still meets Claim 1. Claim 2 covers compositions with a pharmaceutically acceptable diluent or carrier.
4) What is the most critical structural feature to check for a potential carve-out?
The stereochemical configuration at (2S) and the precise chemical descriptor at the pyrrolidinyl functionality (the patent text uses “2-oxy” in Claim 1 and “2-oxo” in Claim 5) plus the presence of the correct 2-oxo/2-oxy-substituted propylpyrrolidine butanamide scaffold.
5) If a drug is approved for neuropathic pain, does that intersect Claim 4?
Yes. Claim 4 explicitly includes neuropathic pain as one of the narrowed conditions, and Claim 3 also includes neuropathic pain in its broader list.
References
[1] US Patent 6,911,461. Claims 1-5 (as provided).
