United States Patent 8,058,291 (Memantine Extended-Release Plus Donepezil): Scope, Claims, and U.S. Landscape
U.S. Patent 8,058,291 claims methods for treating Alzheimer’s disease and dementia (and, in one dependent set, Parkinson’s disease) using once-daily oral extended-release (ER) memantine in combination with donepezil, where ER memantine is characterized by a reduced early exposure slope relative to immediate release (IR) memantine. The differentiator is quantitative: the ER formulation must produce a change in plasma concentration as a function of time (dC/dT) over a defined post-dose window (0 to Tmax of IR memantine) that is less than about 50% of the IR comparator, measured in a single-dose human PK study.
The claims also ladder into formulation and in vitro dissolution and release-mode parameters (monophasic vs biphasic; ethyl cellulose-based extended-release matrix with specific soluble components; dissolution targets by USP<711> type 2 paddle at 37°C).
What is the core claim construct in 8,058,291?
Independent claim architecture
The patent is anchored by two method forms:
- Claim 1 (treatment method): once-daily oral ER memantine (5 to 40 mg) plus therapeutically effective donepezil, for CNS-related conditions selected from Alzheimer’s disease and dementia, with the PK slope limitation on ER memantine vs IR memantine.
- Claim 6 (adverse-effect reduction method): similar combination and ER PK limitation, but framed as reducing potential for an adverse effect related to memantine, with the same CNS selection and ER/IR PK criteria.
A third independent-style set is embedded as Claim 34, which re-states the method and adds a condition group that includes Parkinson’s disease (with Alzheimer’s disease also in the list). Claim 34 retains the same ER PK slope requirement and once-daily dosing range.
Key quantitative PK limitation
Across Claim 1 and Claim 6 (and repeated in Claim 34), the defining limitation is:
- ER memantine produces a dC/dT < about 50% of dC/dT for the same quantity of IR memantine,
- where dC/dT is measured in a single-dose human PK study,
- over the defined period from 0 to Tmax of the IR form.
A later dependent structure tightens the window to:
- “0 to Tmax” = first 6 hours after administration (Claims 53–58).
Dose ranges
ER memantine is limited to:
- 5–40 mg once daily (Claim 1; also echoed in dependent range claims 2–4 and multiple later dependent claims).
Dependent constraints specify narrower ER memantine bands:
- 10–40 mg (Claim 2 and mirrored in other dependents),
- 12.5–40 mg (Claim 3 and multiple later claims),
- 20–40 mg (Claim 40, 51, 52, 35, 48-52 depending on dependency),
- 22.5–40 mg (Claim 48, 49, 52, 49-52),
- and multiple “composition” dependents that effectively replicate these bands in ER/IR blended dosage units (Claims 20–21, 28, 40, 48–52).
Donepezil is limited to:
- 1–20 mg donepezil hydrochloride (Claim 15) in the adverse-effect reduction construct,
- with donepezil pharmacologic form typically immediate release in multiple formulation dependents (Claims 8, 16–19 analogues and Claim 45–47, 38–39).
CNS condition scope
- Claim 1 and Claim 6: CNS-related condition selected from Alzheimer’s disease and dementia.
- Claim 34: CNS-related condition selected from Alzheimer’s disease and Parkinson’s disease.
This creates a split across the claim set: Alzheimer’s coverage is explicit in both, while Parkinson’s appears only in the Claim 34 branch.
What is the full treatment scope (who, what, how) in practical terms?
Patient and administration
- “a human subject in need thereof” with CNS-related condition in the enumerated group.
- Once daily oral administration.
- Memantine is in an extended release dosage form; donepezil is therapeutically effective with several claims specifying immediate release donepezil or co-formulation.
Combination modes
Claim 1 specifies administration/combination permutations that become detailed in dependents:
- Simultaneous administration (Claim 4).
- Single composition co-dosing (Claim 5).
- In the Claim 6 cluster:
- the memantine ER + donepezil are in a single oral pharmaceutical composition (Claim 6),
- the combination can be unit dosage form (Claim 19),
- and can be capsule (Claim 14).
ER vs IR blending in the dosage unit
The patent repeatedly allows partial IR fraction while keeping the majority as ER:
- At least 80% of memantine provided in ER form; remainder IR (Claims 23 and 29; duplicated in Claim 29).
- At least 95% of memantine provided in ER form; remainder IR (Claims 24 and 30; duplicated in Claim 30).
These appear in both the “method of reducing adverse effect” line (Claim 6) and mirrored in later dependents.
What formulation and dissolution boundaries are locked in?
The claims do not just define PK in vivo; they include structural/in vitro release language that constrains the ER platform.
Beads/pellets and extended-release coating
The patent includes dependents requiring ER multiparticulates:
- Memantine is formulated as beads and/or pellets (Claim 9).
- Beads/pellets comprise an extended release coating (Claim 10).
Coating/matrix composition
The extended release coating is constrained to an insoluble matrix polymer plus a soluble material:
- Insoluble matrix polymer:
- ethyl cellulose (Claim 12), and a combined dependent specifying ethyl cellulose (Claim 13).
- Water-soluble material:
- hydroxypropyl methyl cellulose and/or polyvinylpyrrolidone (Claim 13).
This combination is repeated as the selection list (Claims 11–13).
Capsule/unit dose
- Unit dosage form in a capsule (Claim 14).
- Memantine ER beads/pellets inside capsules are consistent with the earlier beads/pellets coating dependents.
Dissolution targets (USP type 2 paddle)
Claim 22 requires specific in vitro dissolution behavior:
- using USP type 2 (paddle) dissolution at:
- 50 rpm, 37 ± 0.5°C, water as medium,
- dissolution limits:
- < 30% in 1 hour
- < 40% in 2 hours
- > 40% in 6 hours
These dissolution numbers tightly define ER performance and provide nonclinical evidence for PK behavior.
Release mode
Release behavior is explicitly constrained:
- monophasic (Claims 25 and 31),
- biphasic (Claims 26 and 32).
Extended-release excipient set
Memantine includes one or more ER excipients:
- ethyl cellulose
- hydroxypropyl methyl cellulose
- polyvinylpyrrolidone
(Claims 27 and 33).
What are the exposure-shaping “profile” claim elements beyond the slope test?
Beyond the dC/dT slope limitation, Claim 18 adds a Cmax-to-cmean ratio window:
- Cmax/cmean about 2.5 to 2
- measured at:
- 1 hour to at least 6 hours after administration.
This adds an additional exposure-shape constraint that can be asserted even if dC/dT is argued.
Tmax shift is also claimed as dependent constraints in Claim 16 and 17:
- shift in memantine Tmax of at least 8 hours vs IR (Claim 16),
- and memantine Tmax at least 19 hours (Claim 17).
How are the dose-unit compositions specified?
Memantine quantity per dose
Within the ER/IR blended unit dosage structure, dependents specify:
- unit dosage 10–40 mg memantine (Claim 7),
- 20–40 mg memantine (Claim 28 and 51),
- 12.5–40 mg memantine hydrochloride (Claim 20),
- at least 22.5 mg memantine hydrochloride (Claim 21),
- and multiple additional dependent restatements (Claims 40, 48–52).
Donepezil quantity and form
- 1–20 mg donepezil hydrochloride (Claim 15).
- Donepezil is immediate release in multiple dependents:
- Claim 8 (donepezil immediate release),
- Claim 38–39 and Claim 45–47 restate immediate release donepezil in the composition/unit dose lines.
What does Claim 34 add compared with Claim 1/6?
Claim 34 adds two scope points:
- It expands the CNS-condition selection to include Parkinson’s disease (the only appearance of Parkinson’s in the provided claim set).
- It restates the ER PK improvement construct with a slightly different framing:
- the “improvement comprising (a) dC/dT < 50% over a defined time period 0 to Tmax of IR memantine” and
- “(b) administered once daily 5–40 mg.”
Claim 34 depends into:
- memantine daily dose 10–40 mg (Claim 35),
- administration as a composition (Claim 36),
- unit dosage form (Claim 37),
- and donepezil immediate release (Claims 38–39).
It also contains another set of ER/IR and timing dependents:
- 0 to Tmax defined as first 6 hours (Claims 55–58),
- memantine dose ranges (Claims 50–52),
- and in some dependents the unit dosage with ER memantine and IR donepezil.
How does this translate into a patent landscape and infringement posture in the U.S.?
What is clearly claim-protectable in the U.S.
Based on the claim text provided, U.S. Patent 8,058,291 is designed to capture competitors that commercialize:
- once-daily oral ER memantine with in vivo exposure shaping (dC/dT reduced to <50% over 0 to IR Tmax, single-dose human PK),
- in combination with donepezil,
- with conditions including Alzheimer’s disease/dementia and (under the Claim 34 branch) Parkinson’s disease,
- and, for broader formulation claim coverage, ER platforms consistent with:
- ethyl cellulose insoluble matrix plus hydroxypropyl methyl cellulose and/or polyvinylpyrrolidone,
- USP dissolution performance thresholds (Claims 22),
- and defined release mode.
What is most likely to drive “yes/no” infringement
For this patent, the most litigable elements are:
- The PK slope limitation: dC/dT < 50% relative to IR memantine at the same quantity over 0 to IR Tmax.
- The dose and once-daily ER administration.
- The combination with donepezil (with multiple claims requiring simultaneous or single composition).
- The donepezil dose/form where those dependents are asserted (e.g., 1–20 mg donepezil HCl; IR donepezil).
- If claim scope is extended into formulation dependents, the beads/pellets + extended-release coating structure and ethyl cellulose-based matrix becomes material.
- If dissolution dependents are asserted, the USP type 2 paddle profile is a practical testable design target.
Design-around levers that map to the claim language
The claim set indicates possible design-around paths, each tied to specific claim elements:
- Avoid the dC/dT limitation: shift ER exposure so that dC/dT over 0 to IR Tmax is not below the <50% threshold.
- Avoid the condition class: if a competing indication strategy narrows away from the enumerated conditions. (This is inherently restricted by medical practice and labeling strategy.)
- Change the dosing form/formulation mode so dependents about coatings, ethyl cellulose, dissolution limits, or release mode are not met.
- Change dosing cadence: claims are “once a day.” Altering dosing frequency could be a nontrivial clinical and labeling change, but it targets the claim preamble.
- Change the combination: claims require donepezil in the specified treatment framework. A monotherapy or a different combination partner not captured in the claim group changes infringement posture.
How to read the claim set as “scope tiers”
Tier 1: PK-defined treatment with donepezil
- Claim 1 (treatment) and Claim 6 (adverse-effect reduction).
- These are the broadest because the defining limitation is PK slope over a defined period.
Tier 2: Dose band tightening
- Multiple dependents set memantine dose windows (10–40, 12.5–40, 20–40, 22.5–40).
Tier 3: Co-formulation structure and unit dose mechanics
- Simultaneous vs single composition.
- Unit dosage forms.
- Capsule form.
- ER beads/pellets with ER coating.
Tier 4: Excipient and dissolution mechanics
- Ethyl cellulose + soluble excipient pair(s).
- USP dissolution thresholds.
Tier 5: Release mode and exposure metrics
- Monophasic or biphasic release.
- Cmax/cmean ratio window.
- Tmax shift constraints.
Key “business” implications
- The patent is not just a combination claim. It requires a specific PK behavior signature for ER memantine, which raises the technical bar for competitors.
- The formulation dependents indicate that the patent is also meant to reach specific ER manufacturing approaches consistent with ethyl cellulose-based systems.
- The repeated dosing ranges and ER fraction thresholds (80% and 95% ER in a unit dose) support enforcement even if a competitor blends ER and IR fractions.
What is missing for a complete U.S. landscape map?
A complete U.S. landscape normally requires bibliographic and legal-status data (assignee, filing/priority dates, prosecution history, continuation family, patent term adjustments, expiration date, and whether there are active reexaminations, PTAB decisions, or litigations). The prompt includes only claim text, not the patent’s legal metadata or citations to earlier/later references.
Because the request is a “detailed analysis of the scope and claims and patent landscape for United States Drug Patent 8,058,291,” the landscape component below stays strictly inside what can be derived from the claim scope itself, not from external legal events.
Key Takeaways
- U.S. Patent 8,058,291 claims once-daily oral ER memantine (5–40 mg) plus donepezil for Alzheimer’s disease/dementia, with a defining PK requirement: ER dC/dT < ~50% vs IR over 0 to IR Tmax in single-dose human PK.
- Claim 34 extends the CNS-condition list to include Parkinson’s disease (in addition to Alzheimer’s disease).
- Scope extends beyond PK: dependent claims lock in formulation mechanics (ethyl cellulose insoluble matrix with hydroxypropyl methyl cellulose and/or polyvinylpyrrolidone), dissolution thresholds (USP type 2 paddle at 37°C), and release mode (monophasic or biphasic).
- The most infringement-sensitive elements are the PK slope limitation and the combination with donepezil; formulation and dissolution dependents provide additional “design-meet” targets.
FAQs
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What is the central differentiator of U.S. Patent 8,058,291 versus an ER/IR combination without PK limits?
The patent requires ER memantine to produce dC/dT < about 50% of IR memantine over 0 to Tmax of IR in a single-dose human PK study, plus once-daily dosing and combination with donepezil.
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Which donepezil form is required in the dependent formulation claims?
Multiple dependents specify immediate release donepezil and quantify it as 1–20 mg donepezil hydrochloride (e.g., Claim 15).
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Does the patent require a specific memantine release mode?
Dependents claim monophasic (Claims 25 and 31) or biphasic (Claims 26 and 32) release, and both options appear as separately claimable features.
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What dissolution test and thresholds are specified?
Claim 22 uses USP type 2 paddle, 50 rpm, 37 ± 0.5°C, water, with targets <30% at 1 hour, <40% at 2 hours, and >40% at 6 hours.
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Where does Parkinson’s disease enter the claim set?
Parkinson’s disease appears in Claim 34 within the CNS selection list; the base Claim 1/6 selection lists Alzheimer’s disease and dementia.
References
[1] U.S. Patent 8,058,291 claim text provided in the prompt.
