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Patent landscape, scope, and claims summary: |
Executive summary
U.S. Patent 8,268,352 is directed to modified-release oral dosage forms built around a dual-retard architecture: (i) micro-matrix particles containing a high-solubility active ingredient plus hydrophobic release-controlling agents, and (ii) a coating of hydrophobic release-controlling agents over those micro-matrix particles, creating a double diffusion barrier to slow release. The independent scope is framed at the system level (dual retard using specific hydrophobic polymer/wax categories and micro-matrix + coating structure), then narrowed through product/process dependent claims and a metformin-specific exemplar with quantitative dissolution/MDT targets.
The claim set is broad in target selection (large enumerated lists of drug actives), but operationally narrow in two ways: (1) the release-control mechanism must be the matrix + coated micro-matrix double barrier using enumerated hydrophobic agents, and (2) for metformin, specific dissolution and in vivo MDT windows are claimed. Patent value for enforcement against generics hinges on whether accused products preserve the same architectural elements (micro-matrix + hydrophobic coating on the same micro-matrix particles) and whether they use covered hydrophobic release controlling agents and/or achieve the claimed metformin performance criteria.
U.S. Patent 8,268,352 claim chart and claim-by-claim scope
Core invention
A modified-release dosage form comprising:
- Micro matrix particles with high solubility active ingredient + hydrophobic release controlling agents.
- Coating of one or more hydrophobic release controlling agents on those micro matrix particles.
- The combination forms a double barrier to diffusion.
- Dual retard is defined as matrix formulation + reservoir formulation.
Claim 1 (independent, system-level coverage)
- Modified-release dosage form for a high solubility active ingredient.
- Dual retard technique = matrix formulation + reservoir formulation.
- Dosage form includes:
- (a) micro matrix particles containing active + hydrophobic release controlling agent(s).
- (b) coating of hydrophobic release controlling agent(s) on micro matrix particles.
- Double barrier to diffusion.
- Hydrophobic release controlling agents are selected from a long list comprising:
- Copolymer block options such as poly(ethyl acrylate, methyl methacrylate, trimethylammonioethyl methacrylate chloride) with defined ratios (notably 1:2:0.1 and 1:2:0.2).
- A broad set of hydrophobic polymers (e.g., ethylcellulose, ethylcellulose-related cellulose esters, poly(methyl methacrylate), polymethacrylates, etc.).
- Waxes and fatty alcohols and fatty acid esters (beeswax, carnauba, microcrystalline wax, ozokerite, cetostearyl alcohol, stearyl alcohol, cetyl alcohol, myristyl alcohol; glyceryl monostearate, monooleate, tristearin, tripalmitin, glyceryl behenate, hydrogenated castor oil, etc.).
- Active ingredient amount: ≤ 1500 mg.
Interpretation for enforcement
- A defendant design-around can attempt to avoid claim 1 by changing at least one required element:
- remove the coating on micro-matrix particles (single barrier approach), or
- avoid the covered hydrophobic release controlling agents list (use different controlled-release materials outside listed genera or outside listed specific polymers/ratios), or
- use non-“high solubility” actives (though the claim language includes a massive enumeration and uses “high solubility active ingredient,” which typically creates factual disputes over solubility classification).
Claim 2
- Dosage form of claim 1 as a tablet.
Claims 3 and 4 (composition ratios and micro-matrix-to-coating weight ratio)
- Active: hydrophobic agent(s in micro matrix: 100:2.5 to 100:30.
- Micro matrix particles : coating hydrophobic agents: 100:2.5 to 100:30.
These are typical infringement leverage points because generic designs can meet “dual retard architecture” but miss the specific ratio window.
Claim 5 (active ingredient universe, broad enumeration)
- “High solubility active ingredient” from a wide list including major therapeutic categories and many individual drugs; examples in the excerpt include metformin? (not here but is later), plus numerous cardiovascular, antibiotics, NSAIDs, etc.
Claim 6 (additional active ingredient list, includes many explicit drugs)
- Another broad list, with several well-known generic drugs including metformin hydrochloride not in this list (metformin appears in claim 12).
Claim 7 (process claim, micro-matrix preparation + coating)
- Process for preparing the modified-release form:
- Preparing micro matrix particles consisting of high solubility active + hydrophobic release controlling agent(s).
- Coating micro-matrix particles with hydrophobic release controlling agent(s).
Claim 8 (optional co-ingredient; two-active formulations)
- Dosage form optionally includes another active ingredient as immediate or modified release form.
Claim 9 (another active ingredient universe)
- Broad enumeration for the “another active ingredient.”
Claim 10 (further expanded second active ingredient list)
- Additional enumerated actives, including many known pharmaceuticals; this claim increases product flexibility for the asserted dosage form by accommodating combination products.
Claim 11 (alternative dosage forms)
- Dosage form can be multilayered tablet, coated tablet, tablet-in-tablet, or capsule.
Claims 12-21 (metformin-specific dependent set with performance requirements)
These are the strongest infringement anchors because they add quantitative dissolution and in vivo MDT windows.
Claim 12 (metformin exemplar, independent within dependent claim set)
- Modified-release dosage form comprising metformin hydrochloride.
- Uses dual retard with micro matrix particles + hydrophobic coating, with metformin amount ≤ 1500 mg.
- Hydrophobic agent list is similar to claim 1 but includes:
- poly(ethyl acrylate, methyl methacrylate, trimethylammonioethyl methacrylate chloride) ratios,
- poly(ethyl acrylate, methyl methacrylate) ratio,
- ethylcellulose, cellulose esters, methacrylate/methylacrylate polymers,
- waxes, fatty alcohols, and fatty acid esters listed by genus.
Claim 13
Claims 14 and 15
- Metformin: hydrophobic agent(s in micro matrix 100:2.5 to 100:30.
- Micro matrix to coating weight ratio 100:2.5 to 100:30.
Claim 16 (quantitative dissolution window)
- Dissolution of metformin hydrochloride:
- not more than 50% in 1 hour,
- 30% to 90% in 4 hours,
- not less than 65% in 12 hours.
This is a direct testable parameter for litigation and lab comparison.
Claim 17 (in vivo MDT window)
- Once-daily modified release exhibits mean dissolution time (MDT) ~4 to 6 hours.
Claims 18-21 (optional combination, once-daily dosing)
- Optional more than one antidiabetic active ingredient.
- Dosage form can be once a day.
- Once-a-day administration for metformin formulation.
How strong is the patent estate for U.S. Patent 8,268,352? (claim coverage vs design-around)
Strengths
- Architecture-specific: claim 1 requires both micro-matrix particles and a hydrophobic coating on those same particles. This is harder to avoid than generic “extended release” language.
- Material list provides a closed set lever: claim 1’s hydrophobic release controlling agent(s) are chosen from explicit enumerations (including particular polymer families and ratios, plus wax/fatty compositions). In validity or infringement fights, that list can constrain the claim interpretation.
- Metformin dependent claims include functional performance: claims 16 and 17 add quantitative dissolution and in vivo MDT windows, enabling credible non-infringement if an accused product does not meet those performance benchmarks.
Weaknesses / practical vulnerabilities
- Overbreadth in active ingredient listing: claims 5-6 and 9-10 enumerate huge sets of actives across therapeutic categories. That supports broad commercial relevance but also increases attack surface for enablement/utility written-description arguments, depending on the patent’s specification support.
- Potential lack of novelty at the mechanism level: “dual retard” using hydrophobic matrix + reservoir/membrane coating is a known extended-release design strategy in the art. Without a unique mechanistic or compositional differentiator outside the enumerated hydrophobes, claim validity can be challenged on obviousness.
- Performance claims are narrower but easier to test: metformin claims can be designed around by tuning release. If an accused product meets generic dissolution profiles that fall outside the claimed windows, claims 16-17 become weak enforcement targets, even if claim 1 could be asserted.
What prior art is most likely to impact U.S. Patent 8,268,352?
Given only the claim text, the most likely invalidity themes are:
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Extended-release dual barrier systems
- Prior patents and publications on micro-matrix particles coated with hydrophobic polymers/waxes to slow diffusion.
- Systems that create “double barrier” diffusion-controlled release (matrix + coating/membrane) are common.
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Hydrophobic excipient families
- Ethylcellulose, cellulose esters, polymethacrylates, and common waxes and fatty esters are classic controlled-release materials.
- If prior art teaches micro-matrix + hydrophobic coating where the coating is selected from similar excipient sets, obviousness risk increases.
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Metformin modified-release technology
- Metformin HCl extended-release products and their typical dissolution profiles.
- If earlier disclosures already targeted dissolution profiles like “slow first hour” and “substantial release by 12 hours,” claim 16 could be vulnerable unless the patent has a distinctive formulation pathway or results.
Claim interpretation: where infringement is likely to be found
Closest-to-claim match elements for accused products
- Physical structure: micro-matrix particles with hydrophobic content, then a separate hydrophobic coating over those particles.
- Chemistry list: uses hydrophobic release controlling agents from the enumerated set (or equivalents that the court deems insubstantially different).
- Ratios within the stated windows:
- active:hydrophobe in micro-matrix 100:2.5 to 100:30,
- micro-matrix:coating hydrophobe 100:2.5 to 100:30.
- For metformin products: dissolution and MDT must fit claims 16-17.
What generics entry risks exist for metformin once-daily “dual retard” designs?
A generic manufacturer faces two main risk vectors:
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Structural risk (claim 1, 12)
- If the generic preserves micro-matrix particles plus hydrophobic coating on those particles with listed materials and ratios, claim 1/12 exposure increases.
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Performance risk (claims 16-17)
- Even if structure is similar, dissolution and MDT can be decisive.
- A generic that shifts early release above 50% at 1 hour, or drops 12-hour release below 65%, or produces MDT outside ~4-6 hours, can potentially avoid claims 16-17 while still implicating claim 12/1 depending on interpretation.
How does U.S. Patent 8,268,352 compare with typical metformin extended-release patent coverage?
Within the metformin ER landscape, patents commonly cluster into:
- matrix type (hydrophilic vs hydrophobic),
- coatings/membrane layers,
- specific polymers and blending ratios,
- dissolution targets,
- manufacturing processes (granulation, coating, layering).
U.S. 8,268,352 is unusually explicit in:
- defining a dual retard mechanism with micro-matrix + hydrophobic coating and a double barrier concept,
- enumerating a long list of candidate hydrophobic release-controlling materials,
- stating explicit dissolution and MDT windows for metformin.
This combination raises both the potential reach (structure-level system coverage) and the enforceability (metformin numeric windows).
Orange Book / FDA status and Paragraph IV risk
No product-specific Orange Book listing, FDA submission linkage, or Paragraph IV litigation record is provided in the prompt. Without those identifiers tied to particular NDCs/ANDA holders, it is not possible to map 8,268,352 to:
- specific ANDA filings,
- Orange Book listing entries,
- patent codes (P, R, etc.),
- expiration and exclusivity interactions,
- any Paragraph IV settlement or litigation.
Key takeaways
- U.S. Patent 8,268,352 centers on a micro-matrix + hydrophobic coating “double barrier” dual-retard modified-release system.
- Claim 1 (and claim 12 for metformin) is architecture and material-list dependent: micro-matrix particles, a coating on those particles, hydrophobic release-controlling agents selected from enumerated lists.
- Dependent ratio claims (3-4, 14-15) and the metformin performance claims (16-17) are the most concrete infringement and design-around levers.
- The broad drug-actives enumeration expands commercial coverage but can increase vulnerability on enablement/written-description/utility depending on the specification’s breadth support.
FAQs
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What structural features must an accused modified-release product include to infringe claim 1?
A micro-matrix particle containing the high-solubility active and hydrophobic release-controlling agent(s, plus a hydrophobic coating on those micro-matrix particles to form a double diffusion barrier.
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Which claim elements provide the best testable handles for metformin products?
Claims 16-17: the dissolution profile at 1 hour, 4 hours, 12 hours and the in vivo mean dissolution time range.
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How can a generic avoid claims 16-17 while still potentially resembling claim 12?
By tuning formulation to shift dissolution early release above/below the claimed bounds or changing MDT outside 4 to 6 hours, while maintaining or altering structural elements independently.
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Do the enumerated hydrophobic release-controlling agents limit the claim to specific materials?
The claims require selection from the listed categories and specified polymer combinations/ratios and common wax/fatty materials named in the claim text.
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Is the patent mostly about metformin?
No. Metformin is a specific dependent exemplar with numeric dissolution and MDT limitations; claim 1 covers a broader “high solubility active ingredient” universe using the same dual-retard micro-matrix + hydrophobic coating framework.
References (APA)
- U.S. Patent 8,268,352.
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