US Patent 6,849,253: Scope, Claims, Expiration, and Ophthalmic Patent Landscape

US Patent 6,849,253 covers preservative-enhancing aqueous ophthalmic solutions containing a borate-polyol complex, specifically boric acid or a pharmaceutically acceptable borate salt combined with propylene glycol or sorbitol. The broadest claims require the complex at 0.5% to 6.0% by weight and a borate-to-polyol molar ratio of 1:0.1 to 1:10.

The patent’s nominal 20-year term ran from the May 11, 2001 nonprovisional filing date and expired on May 11, 2021, subject to any recorded patent-term adjustment. The claims therefore do not presently create an enforceable US exclusionary right. The patent was primarily relevant to preservative systems for artificial tears, contact-lens solutions, and other aqueous ophthalmic products.

What does US Patent 6,849,253 protect?

US 6,849,253 protects a composition defined by four principal elements:

An aqueous ophthalmic solution.
A water-soluble borate-polyol complex.
A borate-polyol concentration of 0.5% to 6.0% by weight.
A borate-to-polyol molar ratio of 1:0.1 to 1:10.

The patent contains two independent composition claims:

Claim 1 covers propylene glycol as the polyol.
Claim 10 covers sorbitol as the polyol.

The invention is directed to improving the antimicrobial performance of borate-containing ophthalmic solutions without necessarily adding a conventional ophthalmic antimicrobial preservative. The composition can therefore rely on the borate-polyol system as the antimicrobial-enhancing component. [1]

What are the independent claims?

Claim	Polyol	Borate-polyol concentration	Molar ratio	Key limitation
1	Propylene glycol	0.5-6.0 wt.%	1:0.1-1:10	Aqueous ophthalmic solution; antimicrobial enhancement
10	Sorbitol	0.5-6.0 wt.%	1:0.1-1:10	Aqueous ophthalmic solution; antimicrobial enhancement

The independent claims do not require:

A therapeutic active pharmaceutical ingredient.
A specific pH.
A specific tonicity agent.
A particular ophthalmic dosage container.
Hydroxypropyl methylcellulose.
The absence of a conventional antimicrobial agent.

Those features appear only in dependent claims or are not expressly required by the claim language supplied.

How do the dependent claims narrow the patent scope?

Claims 2 through 9 narrow claim 1. Claims 11 through 18 narrow claim 10. The dependent claims create four principal narrowing groups.

Viscosity-enhancing polymer claims

Claims 2 and 11 require an effective amount of a viscosity-enhancing polymer.

Claims 3 and 12 narrow that polymer to a cellulosic polymer.

Claims 4 and 13 further narrow the cellulosic polymer to hydroxypropyl methylcellulose, commonly abbreviated HPMC.

A product containing borate, propylene glycol or sorbitol, water, and HPMC could fall within these dependent claims if it also satisfies the concentration, ratio, and antimicrobial-enhancement limitations.

Antimicrobial-free claims

Claims 5, 9, 14, and 18 require that the solution not contain an ophthalmically acceptable antimicrobial agent.

These claims are narrower than the independent claims. A formulation containing a conventional preservative may avoid these negative limitations while still potentially implicating claims 1 or 10.

The phrase "does not contain an ophthalmically acceptable antimicrobial agent" creates an infringement issue focused on the product’s qualitative composition. Trace impurities, excipients with incidental antimicrobial effects, and the legal meaning of "ophthalmically acceptable antimicrobial agent" could affect claim analysis.

Concentration-limited claims

Claims 6 through 9 and claims 15 through 18 require the borate-polyol complex to be present at 1.0% to 2.5% by weight.

These claims are narrower than the 0.5% to 6.0% range in claims 1 and 10.

Claim group	Concentration	Polyol	Ratio
1, 2-5	0.5-6.0 wt.%	Propylene glycol	1:0.1-1:10
6-9	1.0-2.5 wt.%	Propylene glycol	1:0.1-1:1 or 1:0.25-1:2.5
10, 11-14	0.5-6.0 wt.%	Sorbitol	1:0.1-1:10
15-18	1.0-2.5 wt.%	Sorbitol	1:0.1-1:1 or 1:0.25-1:2.5

Molar-ratio claims

Claims 7 and 16 require a borate-to-polyol ratio of 1:0.1 to 1:1.

Claims 8 and 17 require a ratio of 1:0.25 to 1:2.5.

These ranges overlap. A formulation within 1:0.25 to 1:1 satisfies both narrower ratio limitations, assuming all other limitations are met.

How broad is the literal scope of the patent?

The strongest practical scope is concentrated in formulations containing:

Boric acid or a pharmaceutically acceptable borate salt.
Propylene glycol or sorbitol.
Water.
The claimed concentration range.
The claimed molar ratio.
An ophthalmic intended use.
Antimicrobial enhancement attributable to the complex.

The claims are composition claims, not process claims. They do not expressly cover:

Manufacturing methods.
Sterilization methods.
Packaging systems.
Container-closure designs.
Dosing schedules.
Therapeutic treatment methods.
Use of other polyols such as glycerol, mannitol, xylitol, or polyethylene glycol.

The Markush language in claims 1 and 10 is also important. Claim 1 is limited to propylene glycol, while claim 10 is limited to sorbitol. A formulation using a different polyol would not literally satisfy either independent claim as written, although it could raise doctrine-of-equivalents issues depending on the technical and prosecution history record.

What formulations are protected by US 6,849,253?

The patent potentially covers four commercially relevant formulation profiles.

Propylene glycol formulations

A formulation may fall within claim 1 if it contains:

Water.
Boric acid or a pharmaceutically acceptable borate salt.
Propylene glycol.
0.5% to 6.0% of the borate-polyol complex.
A borate-to-propylene-glycol ratio of 1:0.1 to 1:10.

Claims 6 through 9 provide additional coverage for formulations with 1.0% to 2.5% complex concentration.

Sorbitol formulations

A formulation may fall within claim 10 if it contains:

Water.
Boric acid or a pharmaceutically acceptable borate salt.
Sorbitol.
0.5% to 6.0% of the borate-polyol complex.
A borate-to-sorbitol ratio of 1:0.1 to 1:10.

Claims 15 through 18 address the narrower 1.0% to 2.5% concentration range.

HPMC-containing formulations

HPMC-containing products can implicate claims 4 and 13 if the product also satisfies the parent claim. The presence of HPMC does not independently trigger the patent. It matters only when combined with the claimed borate-polyol system.

Preservative-free formulations

Claims 5, 9, 14, and 18 target products that omit a conventional ophthalmic antimicrobial agent. These claims are commercially relevant to preservative-free artificial tears and contact-lens-related products, but the patent’s expiration removes current US enforcement risk.

When did US Patent 6,849,253 lose exclusivity?

The patent’s nominal expiration date was May 11, 2021.

Event	Date
Earliest listed priority date	May 11, 2000
US nonprovisional filing date	May 11, 2001
US publication	November 21, 2002
Patent grant	February 1, 2005
Nominal patent expiration	May 11, 2021

For a utility patent filed after June 8, 1995, the term generally runs 20 years from the earliest effective US nonprovisional filing date, subject to patent-term adjustment, patent-term extension, terminal disclaimers, and other statutory limitations. [2] The grant date does not determine the expiration date.

No Orange Book exclusivity period follows from this patent alone. Patent expiration also does not remove regulatory requirements applicable to an ophthalmic product, including sterility, quality, labeling, and compliance with the applicable FDA pathway.

What is the Orange Book status of US 6,849,253?

US 6,849,253 is not, by itself, an Orange Book-listed drug patent.

The FDA Orange Book lists patents submitted for approved drug products under Section 505 of the Federal Food, Drug, and Cosmetic Act. [3] US 6,849,253 claims an ophthalmic composition and does not identify a specific approved new drug application in the claim text supplied.

The patent is more likely to have affected:

Over-the-counter artificial tears.
Contact-lens solutions.
Ophthalmic lubricants.
Preservative systems.
Formulation development and freedom-to-operate reviews.

Those products may be regulated through different FDA pathways and may not generate Orange Book patent listings. Absence from the Orange Book does not mean that a formulation lacks patent risk; it means that the patent is not operating through the Orange Book patent-certification mechanism.

Were Paragraph IV challenges relevant?

A conventional Paragraph IV challenge would be relevant only if an abbreviated new drug application referenced an approved drug product for which this patent was properly listed in the Orange Book.

The claims of US 6,849,253 are formulation claims directed to borate-polyol ophthalmic solutions. The more likely commercial pathway involved OTC products, devices, or non-Orange-Book ophthalmic products rather than a classic ANDA dispute.

Because the patent expired in 2021:

A new Paragraph IV challenge would generally have limited practical value against this patent.
A generic or follow-on manufacturer could rely on expiration rather than launch at risk.
Any historical Paragraph IV litigation would need to be evaluated separately from current enforceability.
Patent certification obligations would depend on the referenced product and listing status, not merely on the existence of the patent.

The Hatch-Waxman framework governs abbreviated applications and patent certifications, but it does not convert every formulation patent into an Orange Book patent. [4]

Which companies were commercially exposed?

The patent’s commercial exposure extended to companies developing ophthalmic solutions that combined borate with propylene glycol or sorbitol, especially where HPMC or a preservative-free design was used.

Potentially exposed product categories included:

Product category	Exposure to claim set
Artificial tears with borate and propylene glycol	High technical overlap
Artificial tears with borate and sorbitol	High technical overlap
HPMC-containing lubricant drops	Higher risk under claims 4 and 13
Preservative-free ophthalmic solutions	Higher risk under claims 5, 9, 14, and 18
Products using borate without the claimed polyol	Lower literal overlap
Products using glycerol, mannitol, or xylitol instead of the claimed polyols	Lower literal overlap
Products outside the 0.5%-6.0% complex range	Potential design-around
Non-aqueous ophthalmic formulations	Outside the express aqueous limitation

The patent did not cover every product containing boric acid. The combination, concentration, ratio, and ophthalmic-solution limitations were central.

How strong was the patent estate?

The estate was moderately focused rather than broad.

Strengths

Two independent claims addressed the two commercially relevant polyols identified in the patent: propylene glycol and sorbitol.
The claims covered a relatively broad 0.5% to 6.0% concentration range.
The 1:0.1 to 1:10 molar-ratio range was broad.
Dependent claims added commercially realistic HPMC and preservative-free embodiments.
The claims targeted a formulation function, antimicrobial enhancement, that could be relevant even when no conventional preservative was present.

Limitations

The patent did not cover all polyols.
The claims did not cover a broad genus of borate complexes independent of the specified polyol.
The patent required an aqueous ophthalmic solution.
The claims did not expressly cover manufacturing, packaging, or device features.
The patent expired in 2021.
The antimicrobial-enhancement limitation could create proof issues in litigation if the accused product’s performance did not establish the claimed function.
The borate-polyol concept was exposed to prior-art scrutiny because borate, polyols, and preservative systems were established ophthalmic formulation components before the patent’s filing date.

The patent’s current strength is therefore historical and analytical, not enforceable. Its value lies in freedom-to-operate history, technical lineage, and possible relevance to later patent families.

What patent landscape surrounds the invention?

The surrounding landscape is divided into five technical groups.

Borate-based ophthalmic preservatives

Earlier ophthalmic patents used boric acid and borate salts as buffering, tonicity-adjusting, and antimicrobial-support components. These references form the closest prior-art field because they disclose the same base chemistry and ophthalmic use.

Polyol-containing ophthalmic solutions

Propylene glycol, sorbitol, glycerol, and related polyols were used as humectants, lubricants, tonicity agents, and formulation stabilizers. A patentability analysis would focus on whether the claimed molar ratios and antimicrobial-enhancement function provided a non-obvious distinction over these combinations.

Contact-lens disinfecting systems

Contact-lens solutions often used borate buffers, polyols, surfactants, chelating agents, and antimicrobial preservatives. These products are technically adjacent but may avoid the claims when they use a different antimicrobial system, a different polyol, or different concentration ratios.

Artificial-tear formulations

Artificial tears commonly contain water, viscosity modifiers, electrolytes, borate, and polyols. HPMC-containing lubricant drops represent the closest commercial embodiment for dependent claims 2 through 4 and 11 through 13.

Preservative-free delivery systems

Later innovation shifted toward unit-dose containers, multidose dispensing systems, and antimicrobial-free formulations. These technologies may avoid US 6,849,253 if they do not use the claimed borate-polyol combination or if the preservative-free product falls outside the claimed concentration and ratio ranges.

What generic launch risks exist today?

There is no current US patent-barrier risk from US 6,849,253 because the patent’s nominal term ended in 2021.

A current product review should still distinguish between:

Risk from this expired patent.
Risk from later continuation or divisional patents.
Risk from formulation patents owned by competitors.
Risk from container, device, manufacturing, or sterilization patents.
FDA requirements for ophthalmic sterility and product quality.
Trademark and trade-dress restrictions.
State and federal OTC compliance requirements.

A product that avoided the claims of US 6,849,253 could still infringe a later patent covering a specific artificial-tear formulation, delivery device, preservative system, or manufacturing process.

What licensing deals or litigation affected the patent?

The patent record identified here does not establish a material licensing transaction, settlement agreement, or reported US litigation that remains legally operative after expiration. The patent’s assignee was Alcon Laboratories, Inc., placing the patent within the Alcon ophthalmic formulation portfolio. [1]

Any historical license, covenant not to sue, or settlement would require review of the underlying agreement because those rights can affect past damages, releases, and related patent families even after patent expiration. Patent expiration, however, ends the ability to obtain prospective infringement relief for conduct occurring after expiration.

Key Takeaways

US 6,849,253 covers aqueous ophthalmic solutions containing boric acid or a borate salt with propylene glycol or sorbitol.
The broad concentration range is 0.5% to 6.0% by weight.
The broad molar-ratio range is 1:0.1 to 1:10 borate to polyol.
HPMC, narrower concentrations, narrower ratios, and antimicrobial-free formulations are covered by dependent claims.
The patent’s nominal expiration date was May 11, 2021.
The patent is not an Orange Book patent merely because it covers an ophthalmic formulation.
Paragraph IV exposure was likely limited unless the patent was properly listed against a specific approved drug product.
Current US freedom-to-operate risk from this patent is effectively eliminated by expiration.
Later patents covering formulation, packaging, manufacturing, or delivery technology remain separate risks.

FAQs

Does US 6,849,253 cover boric acid alone?

No. The claims require a borate-polyol complex. Boric acid alone does not satisfy the propylene glycol or sorbitol limitation.

Does the patent cover glycerin or glycerol?

Not literally under the claims supplied. The independent claims specify propylene glycol or sorbitol. Glycerin or glycerol could create a separate equivalence issue, but it is outside the express claim language.

Does adding HPMC create infringement?

HPMC alone does not create infringement. HPMC becomes relevant only when the product also satisfies the borate, polyol, concentration, ratio, aqueous, and ophthalmic-solution limitations.

Can a company sell a product that falls within the expired claims?

Yes, expiration removes the patent’s US exclusionary right. The product must still satisfy applicable FDA, quality, labeling, sterility, and other regulatory requirements.

Is a preservative-free artificial tear automatically covered?

No. Preservative-free status is only one limitation in certain dependent claims. The product must also contain the specified borate-polyol complex within the claimed concentration and molar-ratio ranges.

References

Alcon Laboratories, Inc. (2005). Ophthalmic compositions containing borate-polyol complexes (U.S. Patent No. 6,849,253). U.S. Patent and Trademark Office.
U.S. Patent and Trademark Office. (n.d.). Patent term adjustment. https://www.uspto.gov/patents/laws/patent-term-adjustment
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations, Orange Book. https://www.fda.gov/drugs/drug-approvals-and-databases/approved-drug-products-therapeutic-equivalence-evaluations-orange-book
U.S. Code, 35 U.S.C. § 355(j). Abbreviated applications and patent certifications.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	300936	⤷ Start Trial
Australia	4233693	⤷ Start Trial
Australia	674852	⤷ Start Trial
Canada	2132826	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Summary for Patent: 6,849,253