United States Patent 8,486,446: What Is Claimed and Where the Claim Scope Sits in the Rifamycin SV Colon-Release Landscape
What does US Patent 8,486,446 claim, in operational terms?
US 8,486,446 covers an oral, multi-matrix, colon-only release formulation of rifamycin SV that provides controlled release and/or delayed release and does so through a three-component matrix architecture plus an explicit release-in-buffer performance profile (in the dependent and/or system-defining claim set).
The core claim set requires, in combination:
1) Active ingredient
- Rifamycin SV (any form encompassed by the patent’s use of “rifamycin SV” as the active).
2) Dosage form and release pattern
- Oral pharmaceutical composition.
- Controlled release and/or delayed release of rifamycin SV.
- Release takes place solely in the colon.
3) Three-matrix multi-matrix structure
A “multi-matrix structure” with:
- (a) Amphiphilic matrix in which rifamycin SV is incorporated.
- (b) Lipophilic matrix formed by a substance with melting point < 90°C, with the amphiphilic matrix dispersed in this lipophilic matrix.
- (c) Hydrophilic matrix that completes the tri-matrix system.
4) Colon-only release requirement
- “Release of the active ingredient takes place solely in the colon.”
This is not a mere target; it is a claim constraint.
5) Quantitative performance profile in an enteric buffer (Claim 12)
Claim 12 adds a specific release test window using an “enteric buffer at pH 7.2”:
- < about 30% released after one hour of residence.
- > about 80% released after eight hours of residence.
- Still with release solely in the colon.
6) Optional gastro-protective coating (Claim 7–8)
- The formulation may include a gastro-protective coating.
- Coating selection constrained to:
- Acrylic and methacrylic acid esters, and/or
- Cellulose acetate phthalate.
7) Therapeutic use limitations (Claims 9–15)
The patent includes “for treatment of…” medical indication claims, focused on colon pathologies, including:
- Infectious colitis and related disorders (infectious colitis, bacillary dysentery, pseudomembranous colitis).
- Traveler’s diarrhea.
- Diverticular disease and diverticulitis.
- These map to claims 9–11 and then narrower embodiments in claims 13–15.
What is the independent claim language that most defines scope (Claim 1 vs Claim 12)?
Claim 1 defines the core architecture and colon-only release requirement, without the explicit dissolution-time percent thresholds.
Claim 12 restates the architecture and colon-only release requirement while adding numerical release thresholds in pH 7.2 enteric buffer:
- <30% in 1 hour
- >80% in 8 hours
From a freedom-to-operate perspective, Claim 1 is broader on performance but narrower on testable kinetics; Claim 12 is narrower on performance because it locks in specific dissolution/release behavior.
How broad is the “multi-matrix” structural scope? (Matrix components and constraints)
The matrices are defined by function plus constrained materials lists.
Amphiphilic matrix (Claim 4)
Selected from:
- Lecithin
- Polyoxyethylenated sorbitan monooleate
- Sodium lauryl sulphate
- Sodium dioctyl sulphosuccinate
- Ethylene and/or propylene block copolymers
Scope note: These are listed with “selected from,” so alternatives within the list are within claim scope.
Lipophilic matrix (Claim 5)
Selected from:
- Stearic acid
- Beeswax
- Carnauba wax
- Palmitic acid
- Palmitostearate esters
But Claim 1 also imposes an additional structural constraint:
- Lipophilic matrix “is formed by a substance having a melting point of less than 90°C.”
Therefore, even if a lipophilic substance is not in the explicit list, it can still fall within scope if it satisfies “melting point < 90°C” and is used to form the lipophilic matrix, subject to whether the claim interpretation treats “selected from” lists as exclusive when applied (Claim 5 is dependent, so Claim 1 already includes the melting-point condition).
Hydrophilic matrix (Claim 6)
Selected from:
- Hydroxypropylcellulose
- Hydroxypropylmethylcellulose
- Sodium carboxymethylcellulose
- Hydroxyethylcellulose
- Carboxyvinyl polymers
- Polyvinyl alcohol
- Vinyl polymers
- Alginic acid and its salts
- Polysaccharide polymers
What quantitative formulation ranges does the patent lock in?
Claims 2–3 set rifamycin SV loading ranges.
- Claim 2: rifamycin SV 10% to 90% by weight
- Claim 3: rifamycin SV 20% to 60% by weight
These ranges apply to the composition described in Claim 1 (because they depend on Claim 1).
How does the performance requirement operate? (Claim 12 kinetics in pH 7.2 buffer)
Claim 12’s release profile is the most concrete, measurable limiter beyond the “solely in the colon” requirement.
In “enteric buffer at pH 7.2”:
- After 1 hour: release is less than ~30%
- After 8 hours: release is more than ~80%
This does two things for claim scope:
1) It constrains designs that release too early in the buffer environment.
2) It constrains designs that fail to release enough after prolonged residence.
For litigation and validity, these thresholds are the kind of features most commonly compared against dissolution test disclosures in the prior art.
What is covered on coatings?
Claim 7–8 optionally require a gastro-protective coating and limit the coating materials:
- Gastro-protective coating is selected from:
- acrylic and methacrylic acid esters, and/or
- cellulose acetate phthalate.
This is dependent scope, so an accused formulation could avoid these claims by omitting the coating. But if the coating is used, the coating identity becomes material.
What medical-use coverage exists? (Colon pathology indications)
Claims 9–11 and 13–15 keep the indication set concentrated on colon diseases and colon infections:
- Claim 9: “pathologies of the colon”
- Claim 10: infectious colitis and multiple specific related indications:
- infectious colitis
- bacillary dysentery
- pseudomembranous colitis
- travellers’ diarrhoea
- diverticular disease
- diverticulitis
- Claim 11: infections of the colon
- Claim 13–15 narrow further:
- Claim 13: travellers’ diarrhea and diverticulitis
- Claim 14: travellers’ diarrhea
- Claim 15: diverticulitis
From a patent landscape view, these are “use” claims layered on top of the formulation claims; they can still be valuable even where a formulation is close, because infringement can be driven by prescribed use.
How does this position in the patent landscape? (Practical reading of the claim’s “design DNA”)
This patent’s scope is defined by a repeatable formulation design pattern:
- Colon-targeting: “release solely in the colon” and, in Claim 12, pH 7.2 residence-based release thresholds.
- Tri-matrix architecture:
- amphiphilic phase hosting drug,
- lipophilic phase with a low melting-point constraint (<90°C),
- hydrophilic phase for controlled erosion/swelling behavior.
- Material families typical of sustained-release and colon-targeted systems:
- surfactants and amphiphilic emulsifiers (e.g., lecithin, sodium lauryl sulphate),
- waxes/fatty acids (stearic acid, beeswax),
- cellulose and polysaccharides (HPMC, HEC, CMC, alginate).
In the broader rifamycin colon-release space, that combination is the key. Designs that:
- use rifamycin SV,
- are oral,
- deploy tri-matrix architecture with the same role allocations,
- and achieve the claimed release behavior
are the highest risk against the formulation claims.
What would “non-infringing” design-arounds look like under the literal claim reading?
The claim is conjunctive: the architecture, matrices, melting point constraint, rifamycin SV use, and colon-only release must all be satisfied.
Key design-around levers implied by the claim structure:
- Replace the tri-matrix architecture (Claim 1/12 hinge on that multi-matrix structure with dispersed amphiphilic in lipophilic + hydrophilic matrix).
- Eliminate or change the melting point <90°C condition for the lipophilic matrix as claimed.
- Use a different active (but that changes the patent target).
- Fail the performance threshold in Claim 12 if the competitor is within the tri-matrix architecture but releases too early in pH 7.2 buffer.
- Avoid the gastro-protective coating composition lists if using a coating (to escape Claim 7–8).
- Avoid the specific “for treatment” uses if attempting to reduce use-based infringement exposure (but formulation infringement can remain).
Where does the claim sit relative to typical prior art categories (landscape segmentation)?
A robust landscape read typically segments prior art into four buckets, each relevant to this claim’s elements:
1) Rifamycin SV formulations with oral sustained/colonic delivery
- Focus: rifamycin SV as the active and colon-targeting.
2) Multi-matrix controlled-release architectures
- Focus: amphiphilic + lipophilic + hydrophilic systems.
- Key overlap: role-based dispersion and tri-phase matrix.
3) Low melting point lipophilic carriers
- Focus: waxes/fatty acids and melting point thresholds.
4) Enteric/colon release performance in simulated gastric/intestinal fluids
- Focus: release percent vs time in defined buffer (here pH 7.2).
- Key overlap: achieving delayed release profiles rather than immediate pH-trigger release.
Within that segmentation, the most directly “claim-matching” references are those that disclose the tri-matrix structure and rifamycin SV in one system and provide release data corresponding to Claim 12’s numerical thresholds.
Claim-by-claim scope map (quick reference)
| Claim |
Core limitation set |
Scope impact |
| 1 |
Oral rifamycin SV; controlled/delayed release; multi-matrix (amphiphilic drug incorporation + lipophilic matrix from <90°C melting substance with dispersed amphiphilic + hydrophilic matrix); release solely in colon |
Defines the architecture and colon-only release constraint |
| 2 |
Claim 1 + rifamycin SV 10–90 wt% |
Limits drug loading range |
| 3 |
Claim 1 + rifamycin SV 20–60 wt% |
Tighter loading subset |
| 4 |
Claim 1 + amphiphilic matrix chosen from listed surfactants/polymers |
Material subset for amphiphilic phase |
| 5 |
Claim 1 + lipophilic matrix chosen from listed fatty acids/waxes/esters |
Material subset for lipophilic phase |
| 6 |
Claim 1 + hydrophilic matrix chosen from listed hydrophilic polymers/polysaccharides |
Material subset for hydrophilic phase |
| 7 |
Claim 1 + gastro-protective coating |
Adds coating-dependent scope |
| 8 |
Claim 7 + coating chosen from acrylic/methacrylic esters and/or CAP |
Material subset for coating |
| 9 |
Claim 1 + treatment of colon pathologies |
Use-dependent layer |
| 10 |
Claim 1 + infectious colitis and listed indications |
Broader use subset for colon infections |
| 11 |
Claim 1 + infections of the colon |
Alternative use framing |
| 12 |
Claim 1 + pH 7.2 buffer release profile (<30% at 1 hr; >80% at 8 hrs) + colon-only release |
Adds measurable dissolution performance limits |
| 13 |
Claim 10 + travellers’ diarrhea and diverticulitis |
Narrow use |
| 14 |
Claim 10 + travellers’ diarrhea |
Narrow use |
| 15 |
Claim 10 + diverticulitis |
Narrow use |
Key Takeaways
- US 8,486,446’s enforceable center of gravity is the oral rifamycin SV tri-matrix colon-only release design: amphiphilic drug incorporation + lipophilic phase from a <90°C melting substance with dispersed amphiphilic + hydrophilic phase.
- Claim 12 adds the most testable constraint: in pH 7.2 enteric buffer, <30% release at 1 hour and >80% at 8 hours, while still requiring “release solely in the colon.”
- Dependent claims narrow scope via rifamycin SV loading ranges, specific amphiphilic/lipophilic/hydrophilic polymer lists, optional gastro-protective coatings (acrylic/methacrylic esters and/or cellulose acetate phthalate), and colon infection/diverticular and traveler’s diarrhea indications.
FAQs
1) What is the single most restrictive technical limitation in US 8,486,446?
The combination of tri-matrix architecture plus “release solely in the colon”; for testable specifics, Claim 12’s pH 7.2 release thresholds are the most restrictive.
2) Does the patent require a specific lipophilic excipient?
No for Claim 1, because it requires only a lipophilic matrix “formed by a substance having a melting point of less than 90°C.” Dependent Claim 5 lists specific exemplars.
3) Can a formulation avoid infringement by adjusting dissolution timing?
It can at least evade Claim 12 if it does not meet the <30% at 1 hour and >80% at 8 hours thresholds, but Claim 1 still requires colon-only release via the tri-matrix structure.
4) Is a gastro-protective coating mandatory?
No. It is only required for dependent claims 7–8.
5) What diseases are explicitly covered?
Colon-focused indications including infectious colitis, bacillary dysentery, pseudomembranous colitis, travellers’ diarrhoea, diverticular disease, and diverticulitis (with narrower subsets for travelers’ diarrhea and diverticulitis).
References
[1] US Patent 8,486,446. “Oral pharmaceutical composition containing rifamycin SV with multi-matrix structure for controlled/delayed colon release,” claims 1-15.
