Scope and claims of US Patent 8,388,941: borate–sorbitol/propylene glycol–zinc self-preserved ophthalmic compositions (and antimicrobial enhancement methods)
US Patent 8,388,941 is a formulation-focused ophthalmic patent that claims (1) a multi-dose aqueous ophthalmic composition with USP 26 preservative efficacy achieved by a defined self-preserving system and (2) a method for enhancing antimicrobial activity of an aqueous ophthalmic composition by including that same preservative system in combination with a broad set of therapeutic drug classes, including prostaglandin analogs and specifically travoprost.
The patent’s effective claim scope is driven by the “consisting essentially of” preservative-system construct and the narrow numeric ranges for each component (borate, polyol, and zinc chloride-derived Zn2+). This creates a relatively clear “design-around perimeter” around the preservative system, while leaving flexibility around the ophthalmic therapeutic agent so long as it falls within the recited classes or the specifically recited travoprost embodiments.
What patents protect borate–polyol–zinc self-preserved multi-dose ophthalmic compositions like US 8,388,941?
Core claim thesis (what is actually protected)
The protected invention is not a specific glaucoma drug per se. It is a preservative system that provides sufficient antimicrobial activity to meet USP 26 preservative efficacy requirements in a multi-dose ophthalmic product.
Claim 1 sets the baseline:
- Therapeutic agent: a “therapeutically effective amount” of an ophthalmic agent from a defined group:
- beta-blockers
- carbonic anhydrase inhibitors
- prostaglandin analogs
- neuroprotectants
- anti-angiogenesis agents
- quinolones
- anti-inflammatory agents
- growth factors
- immunosuppressant agents
- anti-allergic agents
- Preservative system: “consisting essentially of”
- Borate (one or more borates) at 0.3 to 1.5 w/v%
- Polyol at 0.6 to 2.0 w/v%, where the polyol comprises sorbitol and propylene glycol
- Zinc ions provided by zinc chloride at 0.0005 to 0.005 w/v%
- Preservative efficacy must satisfy USP 26.
From a freedom-to-operate perspective, the claims protect:
- the combination of (i) that specific preservative system and (ii) the claimed classes of ophthalmic therapeutics, in a multi-dose aqueous formulation.
How broad is the therapeutic-agent coverage?
Claim 1 is broad on drug class selection. It is not limited to glaucoma indications. It includes:
- glaucoma-standard agents (beta-blockers, carbonic anhydrase inhibitors, prostaglandin analogs, quinolones)
- broader ocular therapeutic categories (anti-inflammatory, immunosuppressant, anti-allergic, neuroprotectants, anti-angiogenesis agents, growth factors)
But the scope is still constrained to agents that fit within the listed categories and to ophthalmic therapeutic use in a multi-dose self-preserved setting.
How binding are the numeric ranges?
The preservative system is the critical constraint. Numeric ranges are explicit:
- Borate: 0.3–1.5 w/v%
- Polyol (sorbitol + propylene glycol total): 0.6–2.0 w/v%
- Zinc chloride (Zn2+ source): 0.0005–0.005 w/v%
If a competitor moves outside these windows, it is a direct hit at claim coverage.
“Consisting essentially of” meaning in practice
The phrase “preservative system consisting essentially of” is likely to be interpreted to allow:
- small amounts of other components that do not materially affect preservative system function, while still requiring the three essential components and their ranges.
This matters for design-around:
- adding other antimicrobial preservatives (or changing preservative chemistry materially) can risk an “outside the essential system” finding, depending on claim construction.
How do the claims map to specific commercial ophthalmic products (especially travoprost)?
Claim 3 and Claim 8 narrow to travoprost
- Claim 3: Claim 1 where the therapeutic agent is travoprost.
- Claim 8: borate concentration narrowed to 0.5–1.2 w/v% (in the travoprost embodiment).
If travoprost products use a preservative system with:
- borate 0.3–1.5 w/v% (or narrower 0.5–1.2 w/v% depending on embodiment),
- polyol comprising sorbitol + propylene glycol at 0.6–2.0 w/v%,
- zinc chloride-derived Zn2+ at 0.0005–0.005 w/v%,
- and meet USP 26 preservative efficacy in a multi-dose format,
then the claims align strongly.
Practical product-level interpretation
In litigation or licensing, the burden is typically on the accused formulation’s:
- exact borate species and concentration (w/v%)
- polyol composition and whether sorbitol and propylene glycol are both present within the stated polyol concentration
- zinc chloride amount and whether zinc is present in the relevant range
- whether the formulation is aqueous and multi-dose
- USP 26 preservative efficacy performance
This patent is structured so that formulation testing and composition measurement can be outcome-determinative.
What formulations are covered by US 8,388,941 beyond glaucoma drugs?
Claim 1 explicitly includes “ophthalmic therapeutic agent” classes that extend beyond the classic glaucoma trifecta and can cover:
- anti-inflammatory ocular drugs (within the recited “anti-inflammatory agents” group)
- immunosuppressants (within “immunosuppressant agents” group)
- anti-allergic agents
- quinolones (antibiotics) as a class
- neuroprotectants and anti-angiogenesis agents
- growth factors
Scope depends on how those classes are construed in claim construction. The safest read for infringement analysis is:
- if a therapeutic agent falls cleanly into one of the enumerated drug-type baskets, and
- the rest of claim 1’s preservative system requirements are met,
then claim 1 is in play even if the therapeutic indication differs.
What is the exclusivity and expiration exposure timeline for US 8,388,941 in the US?
No expiration or exclusivity timetable is provided in the prompt, and US 8,388,941’s actual expiration requires:
- the patent grant date and filing/provisional history,
- any PTA (Patent Term Adjustment),
- any terminal disclaimers,
- and whether the patent is the basis for listed Orange Book exclusivities for a specific reference listed drug.
Because that information is not included here, a complete, accurate exclusivity timeline cannot be produced from the provided input.
How many claim “design-around” levers does US 8,388,941 provide?
Lever 1: Borate concentration or species
- Outside 0.3–1.5 w/v% borate breaks Claim 1’s numeric limitation.
- A tighter sub-range appears in dependent claims:
- Claims 7/8/9/10: borate 0.5–1.2 w/v%.
If the therapeutic agent is travoprost and the borate sits outside 0.5–1.2 but still within 0.3–1.5, claim 3 may be affected while claim 1 remains potentially relevant.
Lever 2: Polyol composition and concentration
- Polyol must include sorbitol and propylene glycol and total polyol concentration must be 0.6–2.0 w/v%.
- A competitor removing either sorbitol or propylene glycol from the polyol fraction can argue it no longer meets the claim definition.
Lever 3: Zinc source and range
- Zinc ions must be provided by zinc chloride.
- Range: 0.0005–0.005 w/v%.
Using a different zinc salt or operating outside the specified concentration range is a direct path to avoid meeting the zinc limitation, assuming “consisting essentially of” is strictly applied.
Lever 4: USP 26 preservative efficacy performance
Even if concentrations are within range, infringement still requires the preservative system have “sufficient antimicrobial activity to allow the composition to satisfy USP 26 preservative efficacy requirements.”
This is performance-relevant. A formulation may be compositionally similar but fail USP 26 performance, potentially avoiding the “sufficient antimicrobial activity” element.
Lever 5: Multi-dose aqueous ophthalmic context
Claim 1 and dependent composition claims require a multi-dose ophthalmic composition. Single-dose formats may not fit the “multi-dose” limitation, even with the same chemistry.
What does Claim 4 protect: method for enhancing antimicrobial activity with the same system?
Claim 4 is a method claim that tracks Claim 1’s preservative system:
- includes the borate/polyol/zinc system in an aqueous ophthalmic composition,
- requires USP 26 preservative efficacy performance,
- includes a therapeutically effective amount of an ophthalmic therapeutic agent from the same enumerated group as Claim 1.
Dependent claims:
- Claim 6: therapeutic agent is travoprost
- Claim 10: borate concentration 0.5–1.2 w/v%
Method coverage can be used in enforcement where the accused actor performs formulation with intent/technique to enhance preservative performance, not only where a marketed finished product exists.
How does US 8,388,941 compare with typical “self-preserved ophthalmic” patent patterns?
What is typical
Many self-preserved ophthalmic patents focus on:
- specific preservative chemical classes (e.g., cationic polymers, oxidative systems)
- or non-traditional preservatives such as chelators or surfactants
- with performance language tethered to USP or antimicrobial efficacy tests.
What is distinctive here
US 8,388,941 is distinctive because:
- it defines a three-component preservative system with explicit numeric constraints
- it requires both borate and a polyol blend (sorbitol + propylene glycol) and zinc chloride-derived zinc
- it uses “consisting essentially of,” which creates a system-level boundary rather than permitting broad preservative overlays.
This typically makes it easier to map infringement or design-around based on formulation lab analysis rather than only on efficacy outcomes.
What patent-portfolio risks exist for generics or new preservative systems targeting travoprost?
Highest-risk scenario
A generic travoprost multi-dose aqueous product that:
- uses a borate/polyol/zinc preservative system matching the stated ranges,
- meets USP 26 preservative efficacy,
- and falls under claim 3/8 depending on borate concentration,
creates a direct infringement risk on both composition and method theories.
Lower-risk scenario
- A product that meets USP 26 efficacy with a different preservative system (different chemistry or zinc source)
- or that stays outside any one numeric range
reduces claim 1/4 coverage.
Settlement and licensing posture (how this patent is commonly used)
Given claim structure, this patent is typically positioned as:
- a formulation-perimeter patent: a licensing target for entrants using the same “self-preservation” technology
- or a litigation lever to force reformulation where the accused preservative matches the borate/polyol/zinc design.
(Exact enforcement history is not provided in the prompt.)
Key claim chart (US 8,388,941)
| Claim |
What must be present |
What it covers |
| 1 |
Multi-dose aqueous ophthalmic composition; therapeutic agent in listed classes; preservative system “consisting essentially of” borate 0.3–1.5 w/v%; polyol 0.6–2.0 w/v% comprising sorbitol + propylene glycol; zinc ions from zinc chloride 0.0005–0.005 w/v%; USP 26 preservative efficacy |
Broad platform for multi-dose self-preserved ophthalmic therapeutics across enumerated drug classes |
| 2 |
Claim 1; therapeutic agent is a prostaglandin analog |
Narrow class within claim 1 |
| 3 |
Claim 1; therapeutic agent is travoprost |
Narrow product-specific embodiment |
| 4 |
Method: enhance antimicrobial activity by including preservative system (same composition limitations as claim 1) in an aqueous ophthalmic composition; USP 26 efficacy; therapeutic agent from enumerated classes |
Process/method enforcement for formulation enhancing antimicrobial activity |
| 5 |
Claim 4; therapeutic agent is a prostaglandin analog |
Class method embodiment |
| 6 |
Claim 4; therapeutic agent is travoprost |
Travoprost method embodiment |
| 7 |
Claim 1; borate 0.5–1.2 w/v% |
Numeric narrowing on borate |
| 8 |
Claim 3; borate 0.5–1.2 w/v% |
Travoprost plus narrower borate range |
| 9 |
Claim 4; borate 0.5–1.2 w/v% |
Method plus narrower borate range |
| 10 |
Claim 6; borate 0.5–1.2 w/v% |
Travoprost method plus narrower borate range |
Key takeaways
- US 8,388,941 protects a specific self-preserving system in multi-dose aqueous ophthalmic products: borate (0.3–1.5 w/v%) + sorbitol/propylene glycol polyol (0.6–2.0 w/v%) + zinc chloride-derived Zn2+ (0.0005–0.005 w/v%), with performance that meets USP 26 preservative efficacy.
- The therapeutic-agent element is broad in claim 1 but constrained to enumerated ophthalmic drug classes; travoprost is singled out in claims 3 and 6, with an additional borate sub-range in claims 8 and 10.
- Infringement is highly sensitive to formulation composition measurements (exact ranges, polyol identity, zinc salt source) and to USP preservative efficacy.
- The patent’s practical scope is formulation-perimeter protection, producing clear design-around levers: move borate, move polyol composition, change zinc source, or fail USP 26 performance.
FAQs
1) Does US 8,388,941 require a specific borate species, or any borate?
The claim requires “one or more borates” within 0.3–1.5 w/v% (or 0.5–1.2 w/v% in dependent claims). It is the borate fraction concentration and presence that are defined, not a single named borate species in the provided claim text.
2) Can a product use a different zinc salt and still infringe?
Claim 1 requires zinc ions be “provided by zinc chloride” at 0.0005–0.005 w/v%. Changing the zinc source to a different salt can avoid that limitation.
3) If USP 26 preservative efficacy is not met, does infringement still occur?
Claim 1 and claim 4 both require sufficient antimicrobial activity to satisfy USP 26 preservative efficacy requirements. Failure on that performance element prevents literal satisfaction of the claim as written.
4) Are method claims (claim 4) enforceable without marketing the finished ophthalmic product?
Claim 4 is a method of enhancing antimicrobial activity by including the preservative system in an aqueous ophthalmic composition with the required drug classes and USP 26 performance. Enforcement hinges on the method being practiced as claimed.
5) Is the travoprost coverage limited to borate 0.5–1.2 w/v%?
The travoprost specificity exists in claim 3 (any borate within claim 1’s 0.3–1.5 w/v% range), while claims 8/10 add the narrower borate 0.5–1.2 w/v% constraint.
References (APA)
- United States Patent 8,388,941. (n.d.). “Multi-dose, self-preserved ophthalmic compositions and methods of enhancing antimicrobial activity.” Claims 1-10.
